Using Datatypes in Transact-SQL Statements

    To declare the datatype for a column in a table:

CREATE TABLE [[database.]owner.]table_name
(column_name datatype [NOT NULL | NULL]
[, column_name datatype [NOT NULL | NULL]]...)

ALTER TABLE [[database.]owner.]table_name
ADD column_name datatype NULL
[, column_name datatype NULL...]

For complete syntax, see the CREATE TABLE and ALTER TABLE statements.

    To declare the datatype for a local variable:

DECLARE @variable_name datatype
[, @variable_name datatype...]

For complete syntax, see the DECLARE statement.

    To declare the datatype for a parameter in a stored procedure:

CREATE PROCedure [owner.]procedure_name[;number]
[(parameter1 [, parameter2]...[parameter255])]
[{FOR REPLICATION} | {WITH RECOMPILE}
[{[WITH] | [,]} ENCRYPTION]]
AS sql_statements

where

parameter =

@parameter_name datatype [= default] [OUTPUT]

For complete syntax, see the CREATE PROCEDURE statement.

    To change a value from one datatype to another:

CONVERT (datatype[(length)], expression [, style])

For the complete CONVERT function syntax, see the Functions topic.