Read committed Table Hint in SQL Server

The Read committed table hint is used to specify that a query should use the READ COMMITTED isolation level for a specific table. This is useful when the transaction isolation level of the session is different, but we want to particular query to follow read committed behavior.

Syntex

Select * from tablename (READCOMMITTED)

This hint forces the query to use read committed semantics, even if the transaction is running under a different isolation. It is useful when we want to ensure a query does not read uncommitted data (dirty read) but doesn’t need reparable read or phantom read.

Let’s consider a scenario in a retail application where customers can place orders for products. When a customer places an order, the system needs to check the current stock level of the ordered products before confirming the order.

To ensure that the stock level information is up-to-date while still allowing other transactions to modify it, you might use the READCOMMITTED hint in the transaction that retrieves the current stock level:

BEGIN TRANSACTION; DECLARE @CurrentStockLevel INT; -- Retrieve the current stock level with read committed isolation level SELECT @CurrentStockLevel = StockLevel FROM Products WITH (READCOMMITTED) WHERE ProductID = @ProductID; -- Check if there is enough stock to fulfill the order IF @CurrentStockLevel >= @OrderQuantity BEGIN     -- Confirm the order and update the stock level     UPDATE Products     SET StockLevel = StockLevel - @OrderQuantity     WHERE ProductID = @ProductID;     COMMIT TRANSACTION;     PRINT 'Order confirmed successfully.'; END ELSE BEGIN     ROLLBACK TRANSACTION;     PRINT 'Insufficient stock to fulfill the order.'; END

By applying the READCOMMITTED hint in the query that retrieves the current stock level, the system ensures a read committed isolation level, where only committed data is read, thus providing more accurate stock information.