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SQL Variables
In SQL, Variable is engaged to temporarily store and manipulate a value(s) that can be used within a block/set of SQL statement.
Here're the steps to effectively use SQL variables :
1. Variable Declaration
2. Variable Initialization/Assignment
3. Variable usage in statement
1. Variable Declaration :
It is the first step in creating variable >> Specify variable name using the "@" prefix and it's data type, this process is known as 'variable declaration'. Variable is declared using the 'DECLARE' keyword.
Here's the syntax :
DECLARE @variable_name data_type;
Here's an example :
DECLARE @Employee_Id INT;
2. Variable Initialization/Assignment :
It is the second step in creating variable >> Assign a specific value to the declared variable, this process is known as 'variable Initialization' or 'variable assignment'. 'SET' keyword is used to assign a value to the declared variable.
Here's the syntax :
SET @variable_name = value;
Here's an example :
SET @Employee_Id = 5;
3. Variable usage in statement :
Reference the variable within the 'SELECT' statement to retrieve its value. 'SELECT' or 'PRINT' keyword is used to retrieve variable value.
Here's the syntax :
SELECT @variable_name;
PRINT @variable_name;
Here's an example :
SELECT @Employee_Id;
PRINT @Employee_Id;