# Using Constants

#### Accessing and Changing Relational Data

Accessing and Changing Relational Data

# Using Constants

A constant is a symbol that represents a specific data value. The format of a constant depends on the data type of the value it represents. Constants are also called literals. Some examples of constants are:

• Character strings:
``````'O''Brien'
'The level for job_id: %d should be between %d and %d.'
``````
• Unicode strings:
``````N'Michél'
``````
• Binary string constants:
``````0x12Ef
0x69048AEFDD010E
``````
• bit constants are represented by the numbers 0 or 1.

• datetime constants:
``````'April 15, 1998'
'04/15/98'
'14:30:24'
'04:24 PM'
``````
• integer constants:
``````1894
2
``````
• decimal constants:
``````1894.1204
2.0
``````
• float and real constants:
``````101.5E5
0.5E-2
``````
• money constants:
``````\$12
\$542023.14
``````
• uniqueidentifier constants:
``````0xff19966f868b11d0b42d00c04fc964ff
'6F9619FF-8B86-D011-B42D-00C04FC964FF'
``````

For numeric constants, to specify the sign of the numeric value use the unary + and - operators:

``````+\$156.45
-73.52E8
-129.42
+442
``````

Character and Unicode constants are assigned the default collation of the current database, unless you assign a specific collation using the COLLATE clause:

``````'abc' COLLATE French_CI_AI
N'lustig' COLLATE German_Phonebook_CS_AS
``````
##### Using Constants in Transact-SQL

In Transact-SQL, constants can be used in many ways. Here are some examples:

• As a constant value in an arithmetic expression:
``````SELECT Price + \$.10
FROM MyTable
``````
• As the data value a column is compared against in a WHERE clause:
``````SELECT *
FROM MyTable
WHERE LastName = 'O''Brien'
``````
• As the data value to be placed in a variable:
``````SET @DecimalVar = -1200.02
``````
• As the data value that should be placed in a column of the current row. This is specified with the SET clause of the UPDATE statement or the VALUES clause of an INSERT statement:
``````UPDATE MyTable
SET Price = \$99.99
WHERE PartNmbr = 1234

INSERT INTO MyTable VALUES (1235, \$88.88)
``````
• As the character string that specifies the text of the message issued by a PRINT or RAISERROR statement:
``````PRINT 'This is a message.'
``````
• As the value to test for in a conditional statement such as an IF statement or CASE functions:
``````IF (@@SALESTOTAL > \$100000.00)
EXECUTE Give_Bonus_Procedure
``````

Constants

INSERT

Expressions

LIKE

Operators

PRINT

ALTER TABLE

RAISERROR

CREATE TABLE

UPDATE

DELETE

WHERE