How Can I Share Variables Across Multiple SQL Server Queries?

How to Share Variables Across Queries in SQL Server

In SQL Server, there is no concept of global variables as such. However, if you need to reuse certain values across multiple queries or databases, there are several approaches you can consider:

Using Scalar Variables

While you can declare scalar variables within individual queries, these variables are not accessible outside their scope. To use the same variable across multiple queries, you can declare it at the start of your script:

DECLARE @GLOBAL_VAR_1 INT = Value_1
DECLARE @GLOBAL_VAR_2 INT = Value_2

However, this approach can lead to errors if you attempt to use the variables in a different database context.

Using SQLCMD Variables

SQLCMD mode, available in SQL Server Management Studio (SSMS), allows you to define variables that are scoped to the current batch or script. These variables can be accessed using the syntax:

$(variable_name)

To declare a SQLCMD variable:

:setvar variable_name value

For example:

:setvar GLOBAL_VAR_1 10

You can then use this variable in subsequent queries:

SELECT * FROM TABLE WHERE COL_1 = $(GLOBAL_VAR_1)

Note that SQLCMD variables only persist within the same script or batch.

Using Table Variables

Another option is to create a table variable and insert the desired values into it. The table variable can then be joined or queried across multiple batches or databases.

DECLARE @GlobalVars TABLE (
    Name VARCHAR(50),
    Value INT
)

INSERT INTO @GlobalVars (Name, Value)
VALUES ('GLOBAL_VAR_1', 10), ('GLOBAL_VAR_2', 20)

SELECT * FROM TABLE
JOIN @GlobalVars ON TABLE.VarName = @GlobalVars.Name

This approach provides more flexibility and can be used in various scenarios where sharing variables is required.

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