1. Structured Query Language (SQL)
Chapter 5
Structured Query Language (SQL)
Database Systems: Design, Implementation, and Management, Fifth Edition, Rob and Coronel

2. In this chapter, you will learn:
The basic commands and functions of SQL
How SQL is used for data manipulation (to add, modify, delete, and retrieve data)
How to use SQL to query a database to extract useful information
How SQL is used for data administration (to create tables, indexes, and views)
About more advanced SQL features such as updatable views, stored procedures, and triggers
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

3. Introduction to SQL Ideal database language
Create database and table structures
Perform basic data management chores (add, delete, and modify)
Perform complex queries to transform data into useful information
SQL is the ideal DB language
Data definition language
Data manipulation language
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

4. Good Reasons to Study SQL
ANSI standardization effort led to de facto query standard for relational database
Forms basis for present and future DBMS integration efforts
Becomes catalyst in development of distributed databases and database client/server architecture
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

5. Data Definition Commands
Create database structure
Holds all tables and is a collection of physical files stored on disk
DBMS automatically creates tables to store metadata
Database administrator creates structure or schema
Logical group of tables or logical database
Groups tables by owner
Enforces security
CREATE SCHEMA AUTHORIZATION <creator>
Example: CREATE SCHEMA AUTHORIZATION JONES
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

6. Creating Table Structure
Tables store end-user data
May be based on data dictionary entries
CREATE TABLE <table name> (<attribute1 name and attribute1 characteristics, attribute2 name and attribute2 characteristics, attribute3 name and attribute3 characteristics, primary key designation, foreign key designation and foreign key requirement>);
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

7. Using Domains Domain is set of permissible values for a column
Definition requires:
Name
Data type
Default value
Domain constraint or condition
CREATE DOMAIN <domain_name> AS DATA_TYPE [DEFAULT <default_value>]
[CHECK (<condition>)]
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

8. SQL Integrity Constraints
Adherence to entity integrity and referential integrity rules is crucial
Entity integrity enforced automatically if primary key specified in CREATE TABLE command sequence
Referential integrity can be enforced in specification of FOREIGN KEY
Other specifications to ensure conditions met:
ON DELETE RESTRICT
ON UPDATE CASCADE
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

9. Data Manipulation Commands
Common SQL Commands
Table 5.3
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

10. Enters data into a table
Data Entry and Saving
Enters data into a table
Saves changes to disk
INSERT INTO <table name>
VALUES (attribute 1 value, attribute 2 value, … etc.);
COMMIT <table names> ;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

11. Listing Table Contents and Other Commands
Allows table contents to be listed
UPDATE command makes data entry corrections
ROLLBACK command restores database back to previous condition if COMMIT hasn’t been used
DELETE command removes table row
SELECT <attribute names> FROM <table names>;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

12. Queries Creating partial listings of table contents
SELECT <column(s)> FROM <table name> WHERE <conditions>;
Table 5.4
Mathematical Operators
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

13. Examples Mathematical operators
Mathematical operators on character attributes
Mathematical operators on dates
SELECT P_DESCRIPT, P_INDATE, P_PRICE, V_CODE
FROM PRODUCT
WHERE V_CODE <> 21344;
SELECT P_CODE,P_DESCRIPT,P_ONHAND,P_MIN,P_PRICE FROM PRODUCT WHERE P_CODE < ‘1558-QWI’;
SELECT P_DESCRIPT,P_ONHAND,P_MIN,P_PRICE,PINDATE FROM PRODUCT WHERE P_INDATE >= ‘01/20/2002’;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

14. Computed Columns
New columns can be created through valid computations or formulas
Formulas may contain mathematical operators
May contain attributes of any tables specified in FROM clause
Alias is alternate name given to table or column in SQL statement
SELECT P_DESCRIPT,P_ONHAND,P_PRICE,P_ONHAND*P_PRICE
AS TOTVALUE
FROM PRODUCT;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

15. Operators Logical: AND, OR, NOT Rules of precedence Special
Conditions within parenthesis executed first
Boolean algebra
Special
BETWEEN - defines limits
IS NULL - checks for nulls
LIKE - checks for similar string
IN - checks for value in a set
EXISTS - opposite of IS NULL
SELECT *
FROM PRODUCT WHERE V_CODE = OR V_CODE = 24288;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

16. Advanced Data Management Commands
ALTER - changes table structure
ADD - adds column
MODIFY - changes column characteristics
Entering data into new column
ALTER TABLE <table name> ADD (<column name> <new column characteristics>);
ALTER TABLE <table name> MODIFY (<column name> <new column characteristics>);
UPDATE PRODUCT SET P_SALECODE = ‘2’ WHERE P_CODE = ‘1546-QQ2’;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

17. Advanced Data Management Commands (con’t.)
Dropping a column
Arithmetic operators and rules of precedence
ALTER TABLE VENDOR DROP COLUMN V_ORDER;
Table 5.5
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

18. Advanced Data Management Commands (con’t.)
Copying parts of tables
Deleting a table from database
Primary and foreign key designation
INSERT INTO <receiving table> <receiving table’s column names> SELECT <column names of the columns to be copied> FROM <contributing table name>;
DROP TABLE PART;
ALTER TABLE LINE
ADD PRIMARY KEY (INV_NUMBER, LINE_NUMBER)
ADD FOREIGN KEY (INV_NUMBER) REFERENCES INVOICE
ADD FOREIGN KEY (PROD_CODE) REFERENCES PRODUCT;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

19. Example Aggregate Function Operations
COUNT
MAX and MIN
SELECT COUNT(DISTINCT V_CODE) FROM PRODUCT;
SELECT COUNT(DISTINCT V_CODE) FROM PRODUCT WHERE P_PRICE <= 10.00;
SELECT MIN(P_PRICE) FROM PRODUCT;
SELECT P_CODE, P_DESCRIPT, P_PRICE FROM PRODUCT WHERE P_PRICE = MAX(P_PRICE);
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

20. Example Aggregate Function Operations (con’t.)
SUM
AVG
SELECT SUM(P_ONHAND * P_PRICE) FROM PRODUCT;
SELECT P_DESCRIPT, P_ONHAND, P_PRICE, V_CODE FROM PRODUCT WHERE P_PRICE > (SELECT AVG(P_PRICE) FROM PRODUCT) ORDER BY P_PRICE DESC;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

21. More Complex Queries and SQL Functions
Ordering a listing
Results ascending by default
Descending order uses DESC
Cascading order sequence
ORDER BY <attributes>
ORDER BY <attributes> DESC
ORDER BY <attribute 1, attribute 2, ...>
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

22. More Complex Queries and SQL Functions (con’t.)
Listing unique values
DISTINCT clause produces list of different values
Aggregate functions
Mathematical summaries
SELECT DISTINCT V_CODE
FROM PRODUCT;
Table 5.6
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

23. More Complex Queries and SQL Functions (con’t.)
Grouping data
Creates frequency distributions
Only valid when used with SQL arithmetic functions
HAVING clause operates like WHERE for grouping output
SELECT P_SALECODE, MIN(P_PRICE) FROM PRODUCT_2 GROUP BY P_SALECODE;
SELECT V_CODE,COUNT(DISTINCT(P_CODE)),AVG(P_PRICE)
FROM PRODUCT_2
GROUP BY V_CODE
HAVING AVG(P_PRICE) < 10;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

24. More Complex Queries and SQL Functions (con’t.)
Virtual tables: creating a view
CREATE VIEW command
Creates logical table existing only in virtual memory
SQL indexes
CREATE VIEW PRODUCT_3 AS SELECT P_DESCRIPT, P_ONHAND, P_PRICE FROM PRODUCT WHERE P_PRICE > 50.00;
CREATE INDEX P_CODEX ON PRODUCT(P_CODE);
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

25. More Complex Queries and SQL Functions (con’t.)
Joining database tables
Data are retrieved from more than one table
Recursive queries joins a table to itself
Outer joins can be used when ‘null’ values need to be included in query result
SELECT PRODUCT.P_DESCRIPT, PRODUCT.P_PRICE,
VENDOR.V_NAME, VENDOR.V_CONTACT,
VENDOR.V_AREACODE, VENDOR.V_PHONE FROM PRODUCT, VENDOR WHERE PRODUCT.V_CODE = VENDOR.V_CODE;
SELECT A.EMP_NUM,A.EMP_LNAME,A.EMP_MGR,
B.EMP_LNAME FROM EMP A, EMP B
WHERE A.EMP_MGR=B.EMP_NUM
ORDER BY A.EMP_MGR
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

26. Updatable Views
Common operation in production environments is use of batch routines to update master table attributes using transaction data
Overnight batch jobs
Not all views are updatable
Restrictions
GROUP BY expressions cannot be used
Cannot use set operators---UNION, INTERSECTION, etc.
Most restrictions based on use of JOINS or group operators in views
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

27. Procedural SQL SQL shortcomings Solutions
Doesn’t support execution of stored procedures based on logical condition
Fails to support looping operations
Solutions
Embedded SQL can be called from within procedural programming languages
Shared Code is isolated and used by all application programs.
Procedural SQL (PL/SQL) stored within the database, executed by DBMS, and invoked by the end user
Triggers
Stored procedures
PL/SQL functions
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

28. Procedural SQL (con’t.)
Procedural SQL allows the use of procedural code and SQL statements that are stored within the database.
The procedural code is executed by the DBMS when it is invoked by the end user.
End users can use procedural SQL (PL/SQL) to create:
Triggers
Stored procedures
PL/SQL functions
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

29. Triggers
Procedural SQL code invoked before or after data row is selected, inserted, or updated
Associated with a database table
Table may have multiple triggers
Executed as part of transaction
Can enforce particular constraints
Automate critical actions and provide warnings for remedial action
Can update values, insert records, and call procedures
Add processing power
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

30. Triggers (con’t.) Oracle example
CREATE OR REPLACE TRIGGER <trigger_name> [BEFORE/AFTER]
[DELETE/INSERT/UPDATE OF <column_name]
ON <table_name> [FOR EACH ROW] BEGIN PL/SQL instructions; …………… END;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

31. Stored Procedures
Named collection of procedural and SQL statements stored in database
Invoked by name
Executed as unit
Invoked with EXEC
CREATE OR REPLACE PROCEDURE procedure_name (argument IN/OUT data-type, etc) IS/AS BEGIN DECLARE variable name and data type PL/SQL or SQL statements; END;
EXEC store_procedure_name
(parameter, parameter, …)
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

32. PL/SQL Stored Functions
Named group of procedural and SQL statements that returns a value
Invoked from within stored procedures or triggers
Cannot be invoked from within SQL statements
CREATE FUNCTION function_name (argument IN data-type, etc) RETURN data-type AS BEGIN PL/SQL statements; RETURN (value); …… END;
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

33. Artist Database ERD and Tables
Figure 5.55
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

34. General Rules Governing Relationships Among Tables
Figure 5.56: M:N, Both Sides Mandatory
Figure 5.57: M:N, Both Sides Optional
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

35. General Rules Governing Relationships Among Tables (Con’t.)
Figure 5.58: M:N, One Side Optional
Figure 5.59: 1:M, Both Sides Mandatory
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

36. General Rules Governing Relationships Among Tables (Con’t.)
Figure 5.60: 1:M, Both Sides Optional
Figure 5.61: 1:M, Many Side Optional, One Side Mandatory
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

37. General Rules Governing Relationships Among Tables (Con’t.)
Figure 5.62: 1:M, One Side Optional, One Side Mandatory
Figure 5.63: 1:1, Both Sides Mandatory
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

38. General Rules Governing Relationships Among Tables (Con’t.)
Figure 5.64: 1:1, Both Sides Optional
Figure 5.65: 1:1, One Side Optional, One Side Mandatory
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel

39. General Rules Governing Relationships Among Tables (Con’t.)
Figure 5.66: Weak Entity, Foreign Key Located in Weak Entity
Figure 5.67: Multivalued Attributes (New Table in 1:M
Relationship, Foreign Key CAR_VIN in the New Table
Database Systems: Design, Implementation, & Management, 5th Edition, Rob & Coronel