Microsoft SQL Server/Variables

Declaration and affectation

Every variable name begins with an at.

• Integer operations:

declare @i int
set @i = 5

declare @j int
set @j = 6

print @i+@j -- displays 11

• Character operations:

declare @k char
set @k = '5'

declare @l char
set @l = '6'

print @k+@l -- displays 56

Types

The possible variable types are similar to the table fields ones:

Characters

Those beginning by "n" are in Unicode format.

char, nchar, nvarchar, ntext, text, varchar.

To save a few memory space, it's possible to set a characters number limit during the declaration:

varchar(255)

The variable of characters maximum size is 2 GB :

varchar(MAX)

Numbers

decimal, int (tinyint, smallint, bigint), float, money, numeric, real, smallmoney.

Dates

date, datetime, datetime2, datetimeoffset, smalldatetime, time.

Personalized types

In addition to the native types, it's possible to create one's own data types with CREATE TYPE.

Type determination

The function SQL_VARIANT_PROPERTY returns a given field type. Example:

SELECT SQL_VARIANT_PROPERTY(Field1, 'BaseType')
FROM table1