What situations in Oracle database will cause the table to be locked?
In Oracle database, it is a common situation that the table is locked, which is usually caused by users performing data operations. Common table lock situations include row-level locking, transaction-level locking, and DDL operations. These situations will be introduced in detail below and corresponding code examples will be given.
-- 事务1 BEGIN UPDATE employees SET salary = salary * 1.1 WHERE department_id = 10 FOR UPDATE; COMMIT; END; -- 事务2 BEGIN UPDATE employees SET salary = salary * 1.2 WHERE employee_id = 100; -- 此时因为employee_id=100被事务1锁定,导致事务2无法执行 END;
-- 事务1 BEGIN UPDATE employees SET salary = salary * 1.1 WHERE department_id = 10; -- 由于使用了事务,整个employees表会被锁定,其他事务无法修改数据 COMMIT; END;
-- 事务1 BEGIN ALTER TABLE employees ADD COLUMN email VARCHAR2(100); -- 由于ALTER TABLE操作,employees表会被锁定,其他事务无法对表进行数据操作 COMMIT; END;
In short, table locking is a common database operation phenomenon. You need to pay attention to avoid unnecessary table locking when writing code to avoid unnecessary table locking. Improve the concurrency performance of the database.
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