1. SQL Training – Advanced Course (Oracle Database)
Duration: 1 Day Thursday

2. Greetings Instructor: Angelina Villa
Web page:

3. Schedule 8:00 am - 4:30pm Lab Sessions: 9:00 am, 1:00 pm, 3:00 pm
Lunch Break: 11:30-12:30 pm
10 minute breaks: 10:00 am, 2:30 pm

4. Goals of the Course Purpose: Using DDL Statements
Creating Schema Objects
Advanced PL/SQL Scripting Techniques

5. Oracle DBMS

6. Logical Structures Tablespaces
A database is divided into logical storage units called tablespaces, which group related logical structures together. One or more datafiles are explicitly created for each tablespace to physically store the data of all logical structures in a tablespace.
Oracle Data Blocks
At the finest level of granularity, Oracle database data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk. The standard block size is specified by the DB_BLOCK_SIZE initialization parameter.
Tablespaces
A database is divided into logical storage units called tablespaces, which group related logical structures together. For example, tablespaces commonly group together all application objects to simplify some administrative operations. One or more datafiles are explicitly created for each tablespace to physically store the data of all logical structures in a tablespace.
Every Oracle database contains a SYSTEM tablespace. Oracle creates them automatically when the database is created.
Oracle Data Blocks
At the finest level of granularity, Oracle database data is stored in data blocks. One data block corresponds to a specific number of bytes of physical database space on disk. The standard block size is specified by the DB_BLOCK_SIZE initialization parameter. A database uses and allocates free database space in Oracle data blocks. Oracle reads and writes data in blocks, so a larger block size could lead to more data transfer per I/O call. The default block size depends on the system architecture, but is generally 8k for UNIX systems. A larger block size is sometimes used for data warehouse systems which access data in larger chunks.

7. Logical Structures (cont)
Schema Overview
A schema is a collection of database objects. A schema is owned by a database user and has the same name as that user. Schema objects are the logical structures that directly refer to the database's data. Schema objects include structures like tables, views, and indexes.
Schema Overview
A schema is a collection of database objects. A schema is owned by a database user and has the same name as that user. Schema objects are the logical structures that directly refer to the database's data. Schema objects include structures like tables, views, and indexes. There is no relationship between a tablespace and a schema. Objects in the same schema can be in different tablespaces, and a tablespace can hold objects from different schemas.

8. Oracle Instance An Oracle database server consists of: Oracle database
The combination of the background processes and memory buffers

9. Instances
PGA is a memory buffer that contains data and control information for a server process. A server process is a process that services a client’s requests. A PGA is created by oracle when a server process is started. The information in a PGA depends on the oracle configuration. The PGA area is a non-shared area of memory created by oracle when a server process is started. The basic difference between SGA and PGA is that PGA cannot be shared between multiple processes in the sense that it is used only for requirements of a particular process whereas the SGA is used for the whole instance and it is shared.

10. Creating/Altering Objects

11. Database Objects

12. Database Objects

13. Schemas and Tablespaces

14. Schemas and Tablespaces

15. Data Concepts

16. Data Independence
Logical Data Independence: The capacity to change the conceptual schema without having to change the external schemas and their application programs.
Physical Data Independence: The capacity to change the internal schema without having to change the conceptual schema.

17. The Relational Database model
Developed by E.F. Codd, C.J. Date (70s)
Table = Entity = Relation
Table row = tuple = instance
Table column = attribute
Table linkage by values
Entity-Relationship Model

18. The Relational Model Each attribute has a unique name within an entity
All entries in the column are examples of it
Each row is unique
Ordering of rows and columns is unimportant
Each position (tuple) is limited to a single entry.

19. Structured Query Language (SQL)
Data Control
(DCL)
Grant
Revoke
User Privileges
Data Definition
(DDL)
Create
Alter
Drop
Tables, Views,
Constraints
Data Manipulation (DML)
Select
Insert
Update
Delete
Retrieve and
Manipulate Data

20. SQL Style Guidelines Some recommendations:
¤ Use lowercase names for tables, columns, etc.
¤ Put a descriptive comment above every table
¤ Write all SQL keywords in uppercase
¤ Follow standard indentation scheme
e.g. indent columns in table declarations by 2-4 spaces
¤ Keep lines to 80 characters or less!
wrap lines in reasonable places

21. SQL Database Objects A SQL Server database has lot of objects like
Tables
Views
Stored Procedures
Functions
Rules
Defaults
Cursors
Triggers

22. Managing Objects Object Definition Creating Objects Altering Objects
Dropping Objects
MetaData
Object Permissions

23. Data Definition Language (DDL)

24. Data Definition Commands
These commands alter the structure of a database
CREATE create a Table, Index, or Database
ALTER modify structure of a Database or Table
DROP delete an entire Table, Index, or Database
RENAME rename a Table

25. Creating Objects CREATE Statement Example: CREATE TABLE customers(
customerID int identity,
customer varchar(50) )

26. Alter statements Used to modify table structure Add new column
Change data type of existing column
Delete a column
Add or remove constraints like foreign key, primary key
Add new column:
Alter table test add grade char(1);
Modify a column data type:
Alter table test alter column grade varchar(10);
Delete a column:
Alter table test drop column grade;

27. Altering Objects ALTER Statement
Example: “Alter a table column to not allow null values.”
UPDATE MyTable SET NullCol = N'some_value' WHERE NullCol IS NULL;
ALTER TABLE MyTable ALTER COLUMN NullCOl NVARCHAR(20) NOT NULL;

28. Altering Objects (cont)
ALTER Statement
Example: “Add a customer phone number to the table”
ALTER TABLE customers
ADD customerPhone varchar(40);

29. Dropping Objects
DROP Statement
Example:
DROP TABLE customers;

30. DROP Statement Destroys object forever Object can not be in use
Examples:
DROP TABLE Customers
DROP PROC pr_salesreport

31. Truncate statement TRUNCATE TABLE tablename
Removes all rows in a table
Resets the table
Truncate does the following, where as delete statement does not
Releases the memory used
Resets the identity value
Does not invoke delete trigger

32. How the Programmer Sees the DBMS
Start with DDL to create tables:
Continue with DML to populate tables:
CREATE TABLE Students (
Name CHAR(30)
SSN CHAR(9) PRIMARY KEY NOT NULL,
Category CHAR(20) )
INSERT INTO Students
VALUES(‘Charles’, ‘ ’, ‘undergraduate’)

33. Constraints

34. Constraint Types
Domain
Entity
Referential Integrity

35. Constraints on a Single Relation
not null
unique

primary key

check (P ), where P is a predicate

36. Not Null Constraint CREATE TABLE account ( acct_id CHAR(10) not null,
branch_name CHAR(20) not null,
balance NUMERIC(12, 2) );

37. Unique Constraint CREATE TABLE account ( acct_id CHAR(10),
branch_name CHAR(20),
balance NUMERIC(12, 2),
unique(acct_id, branch_name) );
The unique specification states that the attributes acct_id and branch_name form a candidate key.
Candidate keys are permitted to be null
(in contrast to primary keys).

38. Referential Integrity
Ensures that a value that appears in one relation for a given set of attributes also appears for a set of attributes in another relation.
The primary key clause lists primary key (PK) attributes.
The unique key clause lists candidate key attributes
The foreign key clause lists foreign key (FK) attributes and the name of the relation referenced by the FK.
By default, a FK references PK attributes of the referenced table.

39. Relational Database Management System (RDBMS)
Name Address Parcel #
John Smith 18 Lawyers Dr
T. Brown 14 Summers Tr
Table A
Table B
Parcel # Assessed Value
,000
,000

40. Database Table Keys Definition:
A key of a relation is a subset of attributes with the following attributes:
Unique identification
Non-redundancy

41. Types of Keys PRIMARY KEY FOREIGN KEY
Serves as the row level addressing mechanism in the relational database model.
It can be formed through the combination of several items.
Indicates uniqueness within records or rows in a table.
FOREIGN KEY
A column or set of columns within a table that are required to match those of a primary key of a second table.
the primary key is the only way join relationships can be established.

42. Primary Key Constraint
CREATE TABLE account (
acct_id CHAR(10),
branch_name CHAR(20),
balance NUMERIC(12, 2),
PRIMARY KEY (acct_id) );
¤ Database won’t allow two rows with same account ID

43. Primary Key Constraint (cont)
A primary key can have multiple attributes
CREATE TABLE depositor (
customer_name VARCHAR(30),
acct_id CHAR(10),
PRIMARY KEY (customer_name, acct_id) );
¤ Necessary because SQL tables are multisets
A table cannot have multiple primary keys

44. Foreign Key Constraint
CREATE TABLE location (
l_number INT PRIMARY KEY,
l_name CHAR(200) );
CREATE TABLE department (
d_name CHAR(200),
d_number INT PRIMARY KEY
d_location REFERENCES location(l_number)

45. Enforcing Foreign Keys
If there is a foreign-key constraint from attributes of relation Department to a key of relation Location, two violations are possible:
An insert or update to Department introduces values not found in Location.
A deletion or update to Location causes some tuples of Department to “dangle.”

46. Handling Violations Default : Reject the modification.
Cascade : Make the same changes in department.
Deleted Location : delete department tuple.
Updated Location : change values in department.
Set NULL : Change the department location to NULL.

47. Choosing a Policy
When we declare a foreign key, we may choose policies SET NULL or CASCADE independently for deletions and updates.
Follow the foreign-key declaration by:
ON [UPDATE, DELETE][SET NULL CASCADE]
Two such clauses may be used.
Otherwise, the default (reject) is used.

48. Foreign Key Example CREATE TABLE department ( d_name CHAR(200),
d_number INT PRIMARY KEY);
CREATE TABLE locations (
l_number INT
l_locations CHAR(200),
FOREIGN KEY (l_department)
REFERENCES department(d_number)
ON DELETE SET NULL
ON UPDATE CASCADE);

49. Attribute Constraints
Constraints on the value of a particular attribute.
Add: CHECK( <condition> ) to the declaration for the attribute.
The condition may use the name of the attribute, but any other relation or attribute name must be in a subquery.

50. Check Constraint CREATE TABLE paycheck ( checkno INT, ename CHAR(20),
amount FLOAT,
CHECK ( ename IN
(SELECT name FROM employee)),
CHECK ( amount >= 0.00 ) );

51. Timing of Checks
Attribute-based checks performed only when a values are inserted or updated.
Example:
CHECK (amount >= 0.00)
checks new amount and rejects the modification if the amount is not a defined positive value.
CHECK (ename IN (SELECT name FROM Employee))
not checked if a name is deleted from Employee (unlike foreign-keys).

52. Assertions
An assertion is a predicate expressing a condition that we wish the database always to satisfy.
create assertion <assertion-name> check <predicate>

When an assertion is made, the system tests it for validity, and tests it again on every update that may violate the assertion
may introduce a significant amount of overhead;

Asserting
for all X, P(X)
is achieved in a round-about fashion using
not exists X such that not P(X)

53. Assertion Example
“Every loan has at least one borrower who maintains an account with a minimum balance or $ ”
CREATE ASSERTION balance_constraint
CHECK (NOT EXISTS
(SELECT * FROM loan
WHERE NOT EXISTS
(SELECT * FROM borrower, depositor, account
WHERE loan.loan_number = borrower.loan_number
AND borrower.customer_name = depositor.customer_name
AND depositor.account_number =
account.account_number
AND account.balance >= 1000)))

54. Assertion Example 2
“The salary of an employee must not be greater than the salary of the manager of the department that the employee works for’’
CREAT ASSERTION SALARY_CONSTRAINT
CHECK (NOT EXISTS
(SELECT * FROM employee e, employee m, department d
WHERE e.salary > m.salary
AND e.dno =d.number
AND d.mgrssn = m.ssn))

55. Views

56. Defining Views
Views are relations, except that they are not physically stored.
For presenting different information to different users
Employee(ssn, name, department, project, salary)
Payroll has access to employee, others only to developers
CREATE VIEW developer AS
SELECT name, project
FROM employee
WHERE department = “Development”

57. A Different View Person(name, city)
Purchase(buyer, seller, product, store)
Product(name, maker, category)
We have a new virtual table:
Seattle-view(buyer, seller, product, store)
CREATE VIEW Seattle-view AS
SELECT buyer, seller, product, store
FROM Person, Purchase
WHERE Person.city = “Seattle” AND
Person.name = Purchase.buyer

58. A Different View We can later use the view: SELECT name, store
FROM Seattle-view, Product
WHERE Seattle-view.product = Product.name AND
Product.category = “shoes”

59. What Happens When We Query a View ?
SELECT name, Seattle-view.store
FROM Seattle-view, Product
WHERE Seattle-view.product = Product.name AND
Product.category = “shoes”
SELECT name, Purchase.store
FROM Person, Purchase, Product
WHERE Person.city = “Seattle” AND
Person.name = Purchase.buyer AND
Purchase.poduct = Product.name AND
Product.category = “shoes”

60. Types of Views Virtual views: Materialized views Used in databases
Computed only on-demand – slower at runtime
Always up to date
Materialized views
Used in data warehouses
Precomputed offline – faster at runtime
May have stale data

61. Updating Views
How can I insert a tuple into a table that doesn’t exist?
Employee(ssn, name, department, project, salary)
CREATE VIEW Developers AS
SELECT name, project
FROM Employee
WHERE department = “Development”
If we make the
following insertion:
INSERT INTO Developers VALUES(“Joe”, “Optimizer”)
INSERT INTO Employee VALUES(NULL, “Joe”, NULL, “Optimizer”, NULL)
It becomes:

62. Non-Updatable Views CREATE VIEW Seattle-view AS
SELECT seller, product, store
FROM Person, Purchase
WHERE Person.city = “Seattle” AND
Person.name = Purchase.buyer
How can we add the following tuple to the view?
(“Joe”, “Shoe Model 12345”, “Nine West”)
We need to add “Joe” to Person first, but we don’t have all its attributes

63. Answering Queries Using Views
What if we want to use a set of views to answer a query.
Why?
The obvious reason…
Answering queries over web data sources.

64. Reusing a Materialized View
Suppose I have only the result of SeattleView:
SELECT buyer, seller, product, store
FROM Person, Purchase
WHERE Person.city = ‘Seattle’ AND
Person.per-name = Purchase.buyer
and I want to answer the query
SELECT buyer, seller
Person.per-name = Purchase.buyer AND
Purchase.product=‘gizmo’.
Then, I can rewrite the query using the view.

65. Query Rewriting Using Views
Rewritten query:
SELECT buyer, seller
FROM SeattleView
WHERE product= ‘gizmo’
Original query:
FROM Person, Purchase
WHERE Person.city = ‘Seattle’ AND
Person.per-name = Purchase.buyer AND
Purchase.product=‘gizmo’.

66. Sequences

67. Sequences This creates an auto increment for a column
If a table has a column with sequence or auto increment, the user need not insert data explicitly for the column
Sequence is implemented using the concept of Identity

68. Identity Identity(1,2) Identity has
A seed: initial value
An increment: value by which we skip to fetch next value
Identity(1,2)
will generate sequence numbers 1,3,5,7…

69. Identity (cont) CREATE TABLE table1 ( id integer identity(1,1),
name varchar(10) )
It is enough if we insert like this:
INSERT INTO table1(name) VALUES(‘Ram’);
Ram will automatically assigned value 1 for id

70. Indexing

71. Table Indexing
An Index is a means of expediting the retrieval of data.
Indexes are “built” on a column(s).
Indexes occupy disk space; occasionally a lot.
Indexes aren’t technically necessary for operation and must be maintained by the database administrator.

72. Table Indexing
An Index is a means of expediting the retrieval of data.
Indexes are “built” on a column(s).
Indexes occupy disk space; occasionally a lot.
Indexes aren’t technically necessary for operation and must be maintained by the database administrator.

73. Index-Organized Tables
Regular table access
IOT access
Table access by ROWID
Non-key columns
Index-Organized Tables
Unlike an ordinary (heap-organized) table whose data is stored as an unordered collection (heap), data for an index-organized table (IOT) is stored in a B-tree index structure in a primary key–sorted manner. Besides storing the primary key column values, each index entry in the IOT B-tree stores the non-key column values as well.
Index-organized tables have full table functionality. They support features such as constraints, triggers, LOB and object columns, partitioning, parallel operations, online reorganization, and replication. You can even create indexes on an index-organized table.
Index-organized tables are ideal for OLTP applications, which require fast primary key access and high availability. Queries and DML on an orders table used in online order processing are predominantly primary-key based, and a heavy volume of DML causes fragmentation that results in a frequent need to reorganize. Because an index-organized table can be reorganized online and without invalidating its secondary indexes, the window of unavailability is greatly reduced or eliminated.
An index-organized table is an alternative to:
A table indexed on the primary key by using the CREATE INDEX statement
A cluster table stored in an indexed cluster, which has been created using the CREATE CLUSTER statement that maps the primary key for the table to the cluster key
Key column
Row header
Oracle Database 10g: Administration Workshop II

74. Index Types Clustered index Non-Clustered Index
Controls the physical order of rows
Does not require disk space
One per table (may inc. multiple columns)
Created by default on tables’ Primary Key column
Non-Clustered Index
Physical data structures that facilitate data retrieval
Can have many indexes
Indexes may include many columns

76. Index CREATE INDEX indexname ON tablename(columnname)
This creates a non clustered index on a table
CREATE UNIQUE CLUSTERED INDEX index_name ON Student(sname);
This creates a unique and clustered index on the
Column Sname.

77. Indexes Create an index on name:
B+ trees have fan-out of 100s: max 4 levels !
Adam
Betty
Charles ….
Smith

78. B-Tree Index Example
Commonly used with “attribute” tables as well as “graphic-attribute” tables (CAD data structures)
Binary coding reduces the search list by streaming down the “tree”.
A “balanced” tree is best. 37 12 49 59 19 44 3
Number
High
Low
Primary Key #

79. Clusters Unclustered orders and order_item tables
ORD_NO PROD QTY
101 A
102 A
102 G
102 N
101 A
101 W
Cluster Key
(ORD_NO)
101 ORD_DT CUST_CD
05-JAN-97 R01
PROD QTY A A W
ORD_DT CUST_CD
07-JAN-97 N45 A G N
ORD_NO ORD_DT CUST_CD
JAN R01
JAN N45
Definition of Clusters
A cluster is a group of one or more tables that share the same data blocks because they share common columns and are often used together in join queries. Storing tables in clusters offers the DBA a method to denormalize data. If you implement clustered tables in your database, you do not need to change any application code that accesses the tables. Clusters are transparent to the end user and programmer.
Performance Benefits of Clusters
Disk I/O is reduced and access time improved for joins of clustered tables.
Each cluster key value is stored only once for all the rows of the same key value; therefore, it uses less storage space.
Performance Consideration
Full table scans are generally slower on clustered tables than on nonclustered tables.
Unclustered orders and order_item tables
Clustered orders and order_item tables
Oracle Database 10g: Administration Workshop II

80. Cluster Types Hash cluster Sorted hash cluster Index cluster
Hash function
Hash function 1 2 3
Cluster Types
Index Clusters
An index cluster uses an index, known as the cluster index, to maintain the data within the cluster. The cluster index must be available to store, access, or maintain data in an index cluster.
The cluster index is used to point to the block that contains the rows with a given key value. The structure of a cluster index is similar to that of a normal index.
Although a normal index does not store null key values, cluster indexes store null keys. There is only one entry for each key value in the cluster index. Therefore, a cluster index is likely to be smaller than a normal index on the same set of key values.
Hash Clusters
A hash cluster uses a hash algorithm (either user-defined or system-generated) to calculate the location of a row, both for retrieval and for DML operations.
For equality searches that use the cluster key, a hash cluster can provide greater performance gains than an index cluster because there is only one segment to scan (no index access is needed).
Oracle Database 10g: Administration Workshop II

81. Sorted Hash Cluster SIZE Cluster key 1 Block chain starting points
HASHKEYS …
Cluster key n
Rows sorted by sort key in each block chain
Sorted Hash Cluster: Basic Architecture
In the example in the previous slide, only one table is stored in the sorted hash cluster. Also, the hash function is very simple and no collision is expected. This is because the hash function is determined by the cluster key itself, and each cluster key value is unique. Basically, HASHKEYS represents the number of different originating telephone numbers, and SIZE represents the number of bytes used to store each cluster key metadata.
As you can see, the first part of the sorted hash cluster segment is reserved to store the metadata entries. Each metadata entry contains a link to the list of its corresponding rows. Each list is made up of a series of Oracle blocks that are linked together. Each list is sorted according to the sort key columns.
Whenever you want to retrieve the rows for a corresponding cluster key value, the cluster key value is hashed to its metadata entry location, which gives the sorted list of rows that you are selecting. …
Oracle Database 10g: Administration Workshop II

82. Indexing Overview Index Considerations Best Practices Scenarios:
Can dramatically increase query performance
Adds overhead for index maintenance
Best Practices
Base design on real-world workloads
Scenarios:
Retrieving ranges of data
Retrieving specific values

83. Synonyms

84. Synonyms Allows an alias for :
table, view, sequence, procedure, stored function, package, materialized view, Java class schema object, user-defined object type, or another synonym.
New CREATE SYNONYM syntax

85. Create Synonym

86. Synonym USE tempdb; GO CREATE SYNONYM MyEmployee
FOR Mydb.HumanResources.Employee;
SELECT OBJECTPROPERTYEX(OBJECT_ID('MyEmployee'), 'BaseType') AS BaseType;

87. Public and Private Synonyms
To create a private synonym in your own schema, you must have the CREATE SYNONYM system privilege.
To create a private synonym in another user's schema, you must have the CREATE ANY SYNONYM system privilege.
To create a PUBLIC synonym, you must have the CREATE PUBLIC SYNONYM system privilege.

88. Public Synonyms Public synonyms are accessible to all users.
If dependent tables or dependent valid user- defined object types exist, then you cannot create object of the same name as the synonym in schema.
Do not to create a public synonym with the same name as an existing schema.
PL/SQL units that use that name will be invalidated.

89. Public Synonyms (cont)
CREATE PUBLIC SYNONYM customers
FOR oe.customers;
If the user sh issues the following statement, then the database returns the count of rows from sh.customers:
SELECT COUNT(*) FROM customers;

90. Public Synonyms (cont)
CREATE PUBLIC SYNONYM customers
FOR oe.customers;
If the user sh issues the following statement, then the database returns the count of rows from sh.customers:
SELECT COUNT(*) FROM customers;

91. Public Synonyms (cont)
To retrieve the count of rows from oe.customers, (The user sh must have select permission on oe.customers as well.)
SELECT COUNT(*) FROM oe.customers;
If the user hr's schema does not contain an object named customers, and if hr has select permission on oe.customers:
SELECT COUNT(*) FROM customers;

92. Triggers Associated with a particular table
Automatically executed when a particular event occurs
Insert
Update
Delete
Others

93. Triggers vs. Procedures
Procedures are explicitly executed by a user or application
Triggers are implicitly executed (fired) when the triggering event occurs
Triggers should not be used as a lazy way to invoke a procedure as they are fired every time the event occurs

94. Triggers

95. Triggers
The trigger specification names the trigger and indicates when it will fire
The trigger body contains the PL/SQL code to accomplish whatever task(s) need to be performed

96. Triggers

97. Triggers Timing A triggers timing has to be specified first
Before (most common)
Trigger should be fired before the operation
i.e. before an insert
After
Trigger should be fired after the operation
i.e. after a delete is performed

98. Trigger Events Three types of events are available DML events
DDL events
Database events

99. Trigger Level Two levels for Triggers Row-level trigger
Requires FOR EACH ROW clause
If operation affects multiple rows, trigger fires once for each row affected
Statement-level trigger
DML triggers should be row-level
DDL and Database triggers should not be row-level

100. Event Examples

101. Triggers
Conditions Available So Multiple Operations Can Be Dealt With In Same Trigger
Inserting, Updating, Deleting
Column Prefixes Allow Identification Of Value Changes
New, Old

102. PL/SQL

103. PL/SQL Features Tight integration with SQL Increased performance
Supports data types, functions, pseudo-columns, etc.
Increased performance
A block of statements sent as a single statement
Increased productivity
Same techniques can be used with most Oracle products
Portability
Works on any Oracle platform
Tighter security
Users may access database objects without granted privileges

104. PL/SQL Program Structure
DECLARE
Variable declarations
BEGIN
Program statements
EXCEPTION
Error-handling statements
END;
Variable Declarations
Body
Exception
Section

105. PL/SQL Program Structure (cont)
Execution section
Required
Comment statements
for multi-line comments
/* between */
for single line comments
- - after
/* Script: Student register Purpose: to enroll students in class */
-- Script: Student register -- Purpose: to enroll students
105

106. PL/SQL Program Structure (cont)
106

107. PL/SQL Program Lines May span multiple text editor lines
Each line ends with a semicolon
Text is not case sensitive

108. PL/SQL Variables Variables are local to the code block
Names can be up to 30 characters long and must begin with a character
Declaration is like that in a table
Name then data type the semi-colon
Can be initialized using := operator in the declaration
Can be changed with := in the begin section
Can use constraints
Variables can be composite or collection types
Multiple values of different or same type

109. Common PL/SQL Data Types
CHAR ( max_length )
VARCHAR2 ( max_length )
NUMBER ( precision, scale )
BINARY_INTEGER – more efficient than number
RAW ( max_length )
DATE
BOOLEAN (true, false, null)
Also LONG, LONG RAW and LOB types but the capacity is usually less in PL/SQL than SQL

110. PL/SQL Variable Constraints
NOT NULL
Can not be empty
CONSTANT
Can not be changed

111. PL/SQL Variables Examples
Age number;
Last char ( 10 );
DVal Date := Sysdate;
SID number not null;
Adjust constant number := 1;
CanLoop boolean := true

112. Composite Variables
Data object made up of multiple individual data elements
Composite variable data types include:
RECORD (multiple scalar values similar to a table’s record)
TABLE (tabular structure with multiple columns and rows)
VARRAY (variable-sized array. Tabular structure that can expand or contract based on data values)
A R R A Y
112

113. Reference Variables Directly reference specific database column or row
Assume data type of associated column or row
%TYPE data declaration syntax:
variable_name tablename.fieldname%TYPE;
%ROWTYPE data declaration syntax:
variable_name tablename%ROWTYPE;
113

114. Arithmetic Operators
Parentheses are used to force PL/SQL interpreter to evaluate operations in a certain order
total_hours_worked - 40 * over_time_rate (total_hours_worked – 40) * over_time_rate
114

115. Numeric Functions ABS(Number) CEILING(Number) FLOOR(Number)
Fetches the modulo value of a number
CEILING(Number)
Fetches the closest integer greater than the number
FLOOR(Number)
Fetches the closest integer smaller than the number
EXP(Number)
Fetches the exponent of a number

116. Data Type Conversion Functions
Implicit data conversions
Interpreter automatically converts value from one data type to another
If PL/SQL interpreter unable to implicitly convert value error occurs
Explicit data conversions
Convert variables to different data types
Using data conversion functions
116

117. Data Type Conversion Functions (cont)
TO_DATE: character string to DATE
TO_DATE(‘07/14/01’, ‘MM/DD/YY’);
TO_NUMBER: character string to NUMBER
TO_NUMBER(‘2’);
TO_CHAR: NUMBER or DATE to character string
TO_CHAR(2);
TO_CHAR(SYSDATE, ‘MM/DD/YYYY HH:MI’);

118. Q: What is the final value of variable2?
Assignment Operation
Assigns value to variable
Operator: :=
Syntax: variable_name := value;
String literal within single quotation mark
DECLARE variable1 NUMBER := 0;
variable2 NUMBER := 0;
BEGIN
variable2 := variable1 +1;
END;
Q: What is the final value of variable2?
118

119. Assignment Operation (cont)
String literal within single quotation mark
Examples:
current_s_first_name := ‘Tommy’;
current_student_ID NUMBER := 1111;
Result of adding a value to a NULL value is another NULL value
DEFAULT keyword can be used instead of assignment operator
current_grade NUMBER := DEFAULT;
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120. NULL Values
Until a value is assigned to a variable, the variable’s value is NULL
Performing an operation on a NULL value always results in a NULL value
Advice: Always initialize variable values

121. String Operations Concatenating Joining two separate strings
Operator: || (i.e. double bar)
Syntax:
new_string := string1 || string2;
s_fullname := s_first || s_last;
121

122. String Operations (cont)
Parse
Separate single string consisting of two data items separated by commas or spaces
s_fullname := s_first ||‘ ’|| s_last;
122

123. String Operations (cont)
Variable
Data type
Value
Bldg_code
VARCHAR2 LH
Room_num
101
Room_capacity
NUMBER
150
room_message := bldg_code || ‘ Room ’ || room_num || ‘ has ’ || TO_CHAR(room_capacity) || ‘seats.’;
Question: Write down the value of room_message after the above Assignment statement is executed.
123

124. Arithmetic Operators
Example
Result

125. String Functions LTRIM function RTRIM function
Remove blank leading spaces
string := LTRIM(string_variable_name);
RTRIM function
Remove blank trailing spaces
string := RTRIM(string_variable_name);
125

126. String Functions (cont)
DECLARE
s_address CHAR(20) := ‘951 Rainbow Dr’;
BEGIN
s_address := RTRIM(s_address);
END;
Question: How many characters will be removed from the string assigned to the s_address variable when the RTRIM function in the avove PL/SQL block is executed
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127. String Functions (cont)
LENGTH function syntax
string_length := LENGTH(string_variable_name);
Example:
code_length AS NUMBER(3):= LENGTH(bldg_code);
Question 1: What will be the value of code_length if bldg_code’s value is ‘CR’?
Question 2: What will be the value of code_length if bldg_code’s value is ‘BUS ’?
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128. String Functions (cont)
Modify case of character strings
UPPER function syntax:
string := UPPER(string_variable_name);
LOWER function syntax
string := LOWER(string_variable_name);
INITCAP function syntax
string := INITCAP(string_variable_name);
Example:
s_full_name := UPPER(s_full_name);
128

129. String Functions (cont)
INSTR function
Searches string for specific substring
Returns an integer representing starting position of the substring within the original string
Syntax:
start_position := INSTR(original_string, substring);
Example:
blank_position := INSTR(curr_course_no, ‘ ’);
129

130. String Functions (cont)
starting_position := INSTR(greet_messg,'Hello');
blank_position :=
INSTR(‘Sarah Miller’, ‘ ’);

131. String Functions (cont)
SUBSTR function
Extracts specific number of characters from character string starting at given point.
Syntax:
extracted_string :=
SUBSTR(string_variable,starting_point,
number_of_characters);
Example:
curr_dept := SUBSTR(curr_course_no, 1, 3);
131

132. String Question 1
Q1: Assuming that curr_course_no contains ‘MIS 4200’, what will be the value of curr_number when the following statement is executed?
blank_space := INSTR(curr_course_no, ‘ ’);
curr_number := SUBSTR(curr_course_no,
(blank_space + 1), (LENGTH(curr_course_no) - blank_space));
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133. String Question 2
Q2: Assuming that curr_course_no contains ‘MIS 4200’, what will be the value of curr_dept when the following statement is executed?
blank_space := INSTR(curr_course_no, ‘ ’);
curr_dept := SUBSTR((curr_course_no, 1, (blank_space – 1));
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134. PL/SQL Comparison Operators

135. PL/SQL Selection Structures
IF/THEN
IF/END IF:
IF condition THEN
program statements
END IF;
IF/ELSE/END IF:
ELSE
alternate program statements

136. PL/SQL Selection Structures (cont)
IF/ELSIF:
IF condition1 THEN
program statements;
ELSIF condition2 THEN
alternate program statements;
ELSIF condition3 THEN
. . .
ELSE
END IF;

137. Evaluating NULL Conditions in IF/THEN Structures
If a condition evaluates as NULL, then it is FALSE
How can a condition evaluate as NULL?
It uses a BOOLEAN variable that has not been initialized
It uses any other variable that has not been initialized

138. PL/SQL Loops
Loop: repeats one or more program statements multiple times until an exit condition is reached
Pretest loop: exit condition is tested before program statements are executed
Posttest loop: exit condition is tested after program statements are executed

139. LOOP … EXIT Loop LOOP … EXIT LOOP program statements IF condition THEN
END IF;
more program statements
END LOOP;
Pretest OR
Posttest

140. LOOP … EXIT WHEN Loop LOOP program statements EXIT WHEN condition;
END LOOP;
Posttest

141. WHILE Loop WHILE … LOOP WHILE condition LOOP program statements
END LOOP;
Pretest
WHILE … LOOP

142. Numeric FOR Loop FOR counter_variable IN start_value .. end_value LOOP
program statements
END LOOP;
Preset number of iterations

143. Using SQL Commands in PL/SQL Programs

144. Cursor

145. Cursor A pointer to memory location on database server Used to:
Retrieve and manipulate database data in PL/SQL programs
Types:
Implicit cursor
Explicit cursor

146. Number of rows processed
Cursors
Database Server Memory
Cursor
Number of rows processed
Parsed command
statement
context
area
active set

147. Implicit Cursors
Created automatically every time you use an INSERT, UPDATE, DELETE, or SELECT command
Doesn’t need to be declared
Can be used to assign the output of a SELECT command to one or more PL/SQL variables
Can only be used if query returns one and only one record

148. Implicit Cursors (cont)
Context area
A memory location created by INSERT, UPDATE, DELETE, or SELECT
Contains information about query (# rows, etc.)
Active set
Set of data rows that query retrieves from SELECT
Implicit cursor
A pointer to the context area
Used to assign output of SELECT query to PL/SQL program variables when query will return only one record*
* Error occurs if query returns no records or more than one record

149. Implicit Cursors (cont)
To retrieve data using implicit cursor in PL/SQL, you add an INTO clause to the SELECT query
SELECT field1, field2, ...
INTO variable1, variable2, ...
FROM table1, table2, ...
WHERE join_conditions
AND search_condition_to_retrieve_1_record;
Variables must be declared in Declaration section
Variables must have same data types as fields
To avoid errors, %TYPE reference data type should be used

150. Explicit Cursors
Retrieve and display data in PL/SQL programs for query that might:
Retrieve multiple records
Return no records at all
Must explicitly write the code to:
Declare cursor
Open cursor
Fetch data rows
Close cursor

151. Explicit Cursors (cont)
Must be declared in program DECLARE section
Can be used to assign the output of a SELECT command to one or more PL/SQL variables
Can be used if query returns multiple records or no records

152. Explicit Cursors (cont)
Declare explicit cursor syntax:
CURSOR cursor_name IS select_query;
Open explicit cursor syntax:
OPEN cursor_name;
Fetch values using LOOP…EXIT WHEN loop:
LOOP
FETCH cursor_name INTO
variable_name(s);
EXIT WHEN cursor_name%NOTFOUND;
Close cursor syntax:
CLOSE cursor_name;
Note: When the cursor is declared, system doesn’t check errors in the query. It creates the memory structure to store the active set. The PL/SQL interpreter checks for error and interprets the query when opening the cursor

153. Using an Explicit Cursor
Declare the cursor
Open the cursor
Fetch the cursor result into PL/SQL program variables
Close the cursor

154. Declaring an Explicit Cursor
DECLARE
CURSOR cursor_name IS SELECT_statement;

155. Opening an Explicit Cursor
OPEN cursor_name;

156. Fetching Explicit Cursor Records
FETCH cursor_name INTO variable_name(s);

157. Closing an Explicit Cursor
CLOSE cursor_name;

158. Processing an Explicit Cursor
LOOP ..EXIT WHEN approach:
OPEN cursor_name;
LOOP
FETCH cursor_name INTO variable_name(s);
EXIT WHEN cursor_name%NOTFOUND:
END LOOP;
CLOSE cursor_name;

159. Processing an Explicit Cursor (cont)
Cursor FOR Loop approach:
FOR variable_name(s) in cursor_name LOOP
additional processing statements;
END LOOP;

160. Using Reference Data Types in Explicit Cursor Processing
Declaring a ROWTYPE reference variable:
DECLARE
reference_variable_name cursor_name%ROWTYPE;
Referencing a ROWTYPE reference variable:
reference_variable_name.database_field_name

161. Explicit Cursor Attributes

162. Error Handling

163. Runtime Errors in PL/SQL Programs
Occur when an exception (unwanted event) is raised
Cause program to fail during execution
Possible causes (exceptions):
Division by zero - inserting incompatible data
Constraint violation - retrieving 0/several rows with implicit cursor

164. Handling Runtime Errors in PL/SQL Programs
Exception handling
Programmers place commands in EXCEPTION section
Handle exception options
Correct error without notifying user of problem
Inform user of error without taking corrective action
After exception handler executes
Program ends
DECLARE variable declarations BEGIN program statements EXCEPTION error-handling statements END;

165. Types of Errors in PL/SQL Programs
Handling error procedure depends the type of exception:
Predefined exception
undefined exception
User-defined exception

166. Predefined Exceptions
Common errors that have been given predefined names that appear instead of error numbers

167. Exception Handler Syntax For Predefined Exceptions
WHEN exception1_name THEN
exception handling statements;
WHEN exception2_name THEN …
WHEN OTHERS THEN

168. Undefined Exceptions
Less-common errors that have not been given predefined names
ORA- error code appears
Exception handler tests for ORA- error code and provides alternate error message

169. User-Defined Exceptions
Errors that will not cause a run-time error, but will violate business rules
Programmer creates a custom error message

170. Nested PL/SQL Program Blocks
An inner program block can be nested within an outer program block
DECLARE
variable declarations
BEGIN
program statements
EXCEPTION
error handling statements
END;
Outer
block
DECLARE
variable declarations
BEGIN
program statements
EXCEPTION
error handling statements
END;
Inner
block

171. Exception Handling in Nest Program Blocks
If an exception is raised and handled in an inner block, program execution resumes in the outer block

172. Exception Handling in Nested Program Blocks (cont)
DECLARE
variable declarations
BEGIN
program statements
additional program statements
EXCEPTION
error handling statements
END;
DECLARE
exception_A
BEGIN
RAISE exception_A
EXCEPTION
exception_A error handler
END;
Exception is raised and
handled in inner block
Program execution
resumes here

173. Exception Handling in Nested Program Blocks (cont)
Exceptions raised in inner blocks can be handled by exception handlers in outer blocks

174. Structure of Exception Section

175. Stored Procedures

176. Stored Procedures The first line is called the Procedure Specification
The remainder is the Procedure Body
A procedure is compiled and loaded in the database as an object
Procedures can have parameters passed to them

177. Stored Procedures Run a procedure with the PL/SQL EXECUTE command
Parameters are enclosed in parentheses

178. Stored Functions
Like a procedure except they return a single value

179. PL/SQL Tables Key Value 1 Shadow 2 Dusty 3 Sassy
Data structure that contains multiple data items that are the same data type
Each table item has a key and a value
Key values do not need to be sequential
Used to create a lookup table that is stored in memory to improve processing speed

180. PL/SQL Tables Key Value 1 Shadow 2 Dusty 3 Sassy
Data structure that contains multiple data items that are the same data type
Each table item has a key and a value
Key values do not need to be sequential
Used to create a lookup table that is stored in memory to improve processing speed

181. PL/SQL Table of Records
PL/SQL table that can store multiple values that are referenced by a key
Usually used to store database records that need to be processed by a PL/SQL program
Improves performance by limiting number of database retrievals

182. Using SQL Commands in PL/SQL Programs

183. DML Events
Changes to data in a table
Insert
Update
Delete

184. Using SQL Queries Use SQL action query
Put query or command in PL/SQL program
Use same syntax as the syntax used to execute query or command in SQL*Plus
Can use variables instead of literal values like ‘Tammy’
To specify data values
184

185. Batching SQL and deferring fetching
Execute SQL queries in Stored Procedures
Fetch as needed from the client
You want to “batch SQL” – multiple SQL statements in one PL/SQL anonymous block
Solution: Use REF CURSORS and Anonymous PL/SQL

186. REF Cursors Characteristics Advantages
Pointer to result set on server side
Read only
Forward only
Advantages
Input REF Cursor parameters
Retrieve multiple REF Cursors in a single round trip

187. Anonymous PL/SQL Executes multiple SQL statements in a single batch
Saves DB round trips
Execute as CommandType.Text
Generate dynamically based on application requirements
// C#
string cmdtxt = "BEGIN " +
"OPEN :1 for select * from emp where deptno = 10; " +
"OPEN :2 for select * from dept where deptno = 20; " +
"INSERT INTO DEPT VALUES (50, ‘IT', ‘SAN FRANCISCO');" +
"END;";

188. Using Pre-Defined PL/SQL Packages
DB server provides PL/SQL packages to all of Oracle’s key functionality
Can be used from ODP.NET, similar to any other PL/SQL call
Sample pre-packaged functionality
DBMS_AQ
DBMS_OLAP
DBMS_STREAMS
SDO_GEOM

189. VARRAYs and NESTED TABLES
Newly supported in ODAC 11g
Use Custom Class Code Generation wizard
Check out code samples in directory <OH>\odp.net\samples\2.x\UDT
MyVarrayCustomClass pa = new MyVarrayCustomClass();
pa.Array = new Int32[] { 1, 2, 3, 4 };
pa.StatusArray = new OracleUdtStatus[] {
OracleUdtStatus.NotNull….
param.OracleDbType = OracleDbType.Array;
param.Direction = ParameterDirection.Input;
param.UdtTypeName = “MYVARRAY";
param.Value = pa;

190. Commands at Oracle SQL>
To list all commands:
SQL>help index
To list all tables:
SELECT * FROM case;
To display a table structure:
DESCRIBE tableName
To run a DOS command from Oracle:
HOST DOSCommand
Example: HOST dir
190

191. Creating SQL Command Batch File
Creating a batch file with .sql extension
Syntax: SQL>Edit filename
SQL>edit c:\batch1.sql
Use START command to execute the batch
SQL> START c:\batch1.sql
See the batch file contents at SQL>
SQL>host type c:\batch1.sql
191