In SQL Server, the SESSION_CONTEXT function is used to store and retrieve session-specific information. This can be particularly useful for storing user-specific settings, configurations, or other data that needs to persist throughout the user's session without affecting other users or sessions.
Storing Data in SESSION_CONTEXT
You can store key-value pairs in the session context using the SESSION_CONTEXT function in conjunction with the sp_set_session_context system stored procedure. The procedure allows you to define a key and assign it a value.
Syntax:
EXEC sp_set_session_context @key = 'YourKey', @value = 'YourValue';
Retrieving Data from SESSION_CONTEXT
You can retrieve the stored session context values using the SESSION_CONTEXT() function.
Syntax:
SELECT SESSION_CONTEXT('YourKey') AS YourKeyValue;
Example Usage
1. Setting a Session Context Value:
-- Set session context for the user ID and username
EXEC sp_set_session_context @key = 'UserID', @value = '12345';
EXEC sp_set_session_context @key = 'Username', @value = 'john_doe';
2. Retrieving a Session Context Value:
-- Get the session context values
SELECT
SESSION_CONTEXT('UserID') AS UserID,
SESSION_CONTEXT('Username') AS Username;
3. Using Session Context in Queries:
You can use the session context values to filter data or pass additional parameters in your queries.
-- Example query using session context
SELECT *
FROM Orders
WHERE UserID = SESSION_CONTEXT('UserID');
Notes
- Session context values are stored for the duration of the session and are automatically cleared once the session ends.
- You can set multiple key-value pairs within the same session.
- Session context is unique to each user session - separate users or sessions will not interfere with each other's values.
Using the SESSION_CONTEXT function and sp_set_session_context stored procedure allows you to effectively manage session-specific data in SQL Server, enhancing your application's ability to maintain state across multiple queries within the same session.