1. Managing Tables, Data Integrity, Constraints by Adrienne Watt
5/22/2018
SQL Data Definition
Managing Tables, Data Integrity, Constraints
by Adrienne Watt

2. 5/22/2018
Entering commands
The first step in creating queries (DML or DDL) in SQL Server is to open a new query window.

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Choosing the Database
Once you are ready to enter your command (create table), make sure you are in the correct database. Use the dropdown to select the database.

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Entering the Command
Enter your create table statement. This table will be created in the Adrienne database.

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Datatypes
Before you can continue with creating tables, and constraints, you need to know about datatypes.
Describes type of data allowed
System-supplied datatype
Integers
Bit - Integer data with either a 1 or 0 value.
Int - Integer (whole number) data from -2^31 (-2,147,483,648) through 2^ (2,147,483,647).
Smallint - Integer data from 2^15 (-32,768) through 2^ (32,767).
Tinyint - Integer data from 0 through 255.

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Numeric Datatypes
Decimal - Fixed precision and scale numeric data from -10^38 -1 through 10^38 -1.
Numeric - A synonym for decimal.
Timestamp - A database-wide unique number.
Uniqueidentifier - A globally unique identifier (GUID).
Money
Monetary data values from -2^63 (-922,337,203,685, ) through 2^ (+922,337,203,685, ), with accuracy to a ten- thousandth of a monetary unit.
smallmoney
Monetary data values from -214, through +214, , with accuracy to a ten-thousandth of a monetary unit.

7. More Datatypes Approximate Numbers
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More Datatypes
Approximate Numbers
Float - Floating precision number data from -1.79E through 1.79E
Real - Floating precision number data from -3.40E + 38 through 3.40E
Date and Times
datetime
Date and time data from January 1, 1753, to December 31, 9999, with an accuracy of three-hundredths of a second, or 3.33 milliseconds.
smalldatetime
Date and time data from January 1, 1900, through June 6, 2079, with an accuracy of one minute.

8. More Datatypes Character Strings
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More Datatypes
Character Strings
Char - Fixed-length non-Unicode character data with a maximum length of 8,000 characters.
Varchar - Variable-length non-Unicode data with a maximum of 8,000 characters.
Text - Variable-length non-Unicode data with a maximum length of 2^ (2,147,483,647) characters.
Binary - Fixed-length binary data with a maximum length of 8,000 bytes.
Varbinary - Variable-length binary data with a maximum length of 8,000 bytes.
Image - Variable-length binary data with a maximum length of 2^ (2,147,483,647) bytes.

9. Managing Tables used for storage and manipulation of data
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Managing Tables
used for storage and manipulation of data
contain column, which describe data, rows
table names must follow the rules for naming identifiers
must be unique

10. Create and Modify tables
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Create and Modify tables
Column Name
Unique within the table
Datatype
must be a system datatype or user-defined datatype
Size
Null
Default
value appears in new record only

11. CREATE TABLE Statement
5/22/2018
CREATE TABLE Statement
CREATE TABLE [database.[owner].]table_name (
col_name, column_properties )
table_name
col_name
column_properties
Click on New Query
Enter the following statement into the query screen

12. CREATE TABLE Statement
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CREATE TABLE Statement
USE HOTEL GO i.e. CREATE TABLE tblHotel (HotelNo Int NOT NULL, Name Char(50) NOT NULL, Address Char(50) NULL, City Char(25) NULL ) Press CTRL-E

13. Data Integrity preserves data consistency in a database
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Data Integrity
preserves data consistency in a database
All integrity rules should be stored in the database.
SQL Server supports declarative referential integrity that enforces data integrity automatically as data is inserted, updated, or deleted from a database.
Data integrity falls into four categories:
entity integrity,
domain integrity,
referential integrity,
and user-defined integrity.

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Identity Property
When a new row is added to the table, SQL Server provides a unique, incremental value for that column. Identity columns are often used with the PRIMARY KEY constraints to serve as the unique row identifier for the table. The IDENTITY property can be assigned to a column with a tinyint, smallint, int, decimal, or numeric data type.
generates sequential numbers
does not enforce entity integrity
only one column can have the IDENTITY property
must be defined as an integer, numeric or decimal datatype
cannot update a column with IDENTITY property
cannot contain Null values
cannot bind defaults and default constraints to the column

15. Creating an Identity Column
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Creating an Identity Column
used with the CREATE TABLE statement
IDENTITY[(seed, increment)]
seed – is the initial value of the identity column
increment – is the value to add to the last increment column
i.e. CREATE TABLE tblHotel
(HotelNo Int IDENTITY (1,1),
Name Char(50) NOT NULL,
Address Char(50) NULL,
City Char(25) NULL, ) GO

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Constraints
Constraints are defined to provide data integrity on a table and individual columns in a table. Constraints limit the possible values a user can enter into a table or a column
Constraints are added to a table with Enterprise Manager or typed in query analyzer.

17. Primary Key constraint
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Primary Key constraint
A table can have only one Primary key.
The columns that participate in a Primary key may not accept nulls.
Primary keys may consist of as many as 16 columns.
Primary key constraints cannot be disabled.
[CONSTRAINT constraint_name]
PRIMARY KEY [CLUSTERED | NONCLUSTERED]
(col_name [, col_name2 […, col_name16]])

18. Primary Key Example USE HOTEL97 GO CREATE TABLE tblHotel (
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Primary Key Example
USE HOTEL97 GO
CREATE TABLE tblHotel (
HotelNo Int IDENTITY PRIMARY KEY,
Name Char(50) NOT NULL UNIQUE,
Address Char(50) NULL,
City Char(25) NULL, )
Composite Primary Key
CONSTRAINT claim_key PRIMARY KEY (policy_no, date_reported))

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UNIQUE Constraint
Prevents duplicate values from being entered into a column.
Both PK and UNIQUE constraints are used to enforce entity integrity.
Multiple UNIQUE constraints can be defined for a table.
When a UNIQUE constraint is added to an existing table, the existing data is always validated.
Can be placed on columns that accept nulls. Only one row can be NULL.
Automatically creates a unique index on the selected column.
UNIQUE Constraint Syntax:
[CONSTRAINT constraint_name]
UNIQUE [CLUSTERED | NONCLUSTERED]
(col_name [, col_name2 […, col_name16]])
[ON segment_name]

20. ALTER TABLE Constraint
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ALTER TABLE Constraint
You can use CREATE TABLE and ALTER TABLE statements to add and drop constraints.
ALTER TABLE statement
used to add or drop constraints
does allow columns to be removed
when constraint is added, all existing data is verified for violations

21. UNIQUE constraint example
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UNIQUE constraint example
USE HOTEL97 GO ALTER TABLE tblHotel ADD CONSTRAINT unqName UNIQUE (Name)

22. ALTER TABLE IDENTITY Property
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ALTER TABLE IDENTITY Property
Use ALTER TABLE statement to add a column with the IDENTITY property.
i.e. ALTER TABLE TableName
ADD
ColumnName int IDENTITY(seed, increment)

23. FOREIGN KEY Constraint
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FOREIGN KEY Constraint
defines a column, or combination of columns, whose values match the primary key (PK) of another table.
values in a foreign key (FK) are automatically updated when the PK values in the associated table are updated/changed.
FK constraints must reference PK or the UNIQUE constraint of another table.
number of columns for FK must be same as PK or UNIQUE constraint.
if the WITH NOCHECK option is used, the FK constraint will not validate existing data in a table.
no index is created on the columns that participate in a FK constraint.
FOREIGN KEY Constraint Syntax:
[CONSTRAINT constraint_name]
[FOREIGN KEY (col_name [, col_name2 […, col_name16]])]
REFERENCES [owner.]ref_table [(ref_col [, ref_col2 […, ref_col16]])]

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FOREIGN KEY Example
USE HOTEL97 GO CREATE TABLE tblRoom ( HotelNo Int NOT NULL , RoomNo Int NOT NULL, Type Char(50) NULL, Price Money NULL, PRIMARY KEY (HotelNo, RoomNo), FOREIGN KEY (HotelNo) REFERENCES tblHotel )

25. CHECK Constraint Restricts values that can be entered into a table.
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CHECK Constraint
Restricts values that can be entered into a table.
Can contain search conditions similar to a WHERE clause
Can reference columns in the same table.
The data validation rule for a CHECK constraint must evaluate to a boolean expression.
Can be defined for a column that has a rule bound to it.
CHECK Constraint Syntax:
[CONSTRAINT constraint_name]
CHECK [NOT FOR REPLICATION] (expression)

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CHECK Constraint
USE HOTEL97 GO CREATE TABLE tblRoom ( HotelNo Int NOT NULL, RoomNo Int NOT NULL, Type Char(50) NULL, Price Money NULL, PRIMARY KEY (HotelNo, RoomNo), FOREIGN KEY (HotelNo) REFERENCES tblHotel CONSTRAINT Valid_Type CHECK (Type IN (‘Single’, ‘Double’, ‘Suite’, ‘Executive’)) )

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CHECK Constraint
CREATE TABLE SALESREPS (Empl_num Int Not Null CHECK (Empl_num BETWEEN 101 and 199), Name Char (15), Age Int CHECK (Age >= 21), Quota Money CHECK (Quota >= 0.0), Hire_Date DateTime, CONSTRAINT QuotaCap CHECK ((Hire_Date < “ ”) OR (Quota <=300000)) )

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DEFAULT Constraint
Used to supply a value that is automatically added for a column if the user does not supply one.
A column can have only one DEFAULT.
Cannot be used on columns with timestamp datatype or identity property.
Automatically bound to a column when they are created.
DEFAULT Constraint Syntax
[CONSTRAINT constraint_name]
DEFAULT {constant_expression | niladic-function | NULL}
[FOR col_name]
USE Hotel
ALTER TABLE tblHotel
Add CONSTRAINT df_city DEFAULT ‘Vancouver’ FOR City

29. User-defined Datatypes
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User-defined Datatypes
always based on system-supplied datatype
can enforce data integrity
Length
Allow nulls
Default
Rule

30. Create a user-defined datatype
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Create a user-defined datatype
Choose Types under Programmability in your database.
Right click and choose ‘New’  ‘User-defined datatype’ Or
Execute the sp_addtype system stored procedure.
In a New Query window type:
sp_addtype ssn, 'varchar(11)', 'NOT NULL'
This will add a new user defined data type
called SSN.

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Example
CREATE TABLE SSNTable ( EmployeeID INT Primary Key, EmployeeSSN SSN, CONSTRAINT CheckSSN CHECK (EmployeeSSN LIKE ‘ [0-9][0-9][0-9] - [0-9][0-9] - [0-9][0-9][0-9][0-9] ‘) )

32. Dropping a Table DROP TABLE [database.]owner.]table_name
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Dropping a Table
DROP TABLE [database.]owner.]table_name
Make sure you have the correct database selected
Enter the following statement into a query Window
DROP TABLE tblHotel
Press CTRL+E