-- Hint syntax
/* to master */
Or
/*FORCE_MASTER*/

-- Example
-- Specify the read-write instance to perform the query operation
SELECT /* to master */ * FROM users WHERE user_id = 1;

-- Specify the read-write instance to perform the update operation
UPDATE /* FORCE_MASTER */ orders SET status = 'shipped' WHERE order_id = 1001;

-- Hint syntax
/* to slave */
Or
/*FORCE_SLAVE*/

-- Example
-- Specify a read-only instance to perform the query operation
SELECT /* to slave */ * FROM products WHERE category = 'electronics';

-- Specify a read-only instance to perform the count operation
SELECT /* FORCE_SLAVE */ COUNT(*) FROM transactions WHERE status = 'completed';

-- Specify the read-only analysis engine to perform the query operation 
SELECT /* to ap */ * FROM products WHERE category = 'electronics';

-- Hint syntax
/* to server server_name */

-- Example
-- Specify the instance test_ro_1 to perform the query operation
SELECT /* to server test_ro_1 */ * FROM inventory WHERE product_id = 2002;