mysql高阶语句
MySQL高级语句通常指的是更复杂的数据库操作,如事务管理、存储过程、触发器、视图、索引优化等。以下是一些常见的高级语句和相应的示例代码:
- 事务管理:
START TRANSACTION;
UPDATE accounts SET balance = balance - 100 WHERE account_id = 1;
UPDATE accounts SET balance = balance + 100 WHERE account_id = 2;
COMMIT;
- 存储过程:
DELIMITER //
CREATE PROCEDURE UpdateAccount(IN from_account_id INT, IN to_account_id INT, IN amount DECIMAL(10, 2))
BEGIN
UPDATE accounts SET balance = balance - amount WHERE account_id = from_account_id;
UPDATE accounts SET balance = balance + amount WHERE account_id = to_account_id;
END //
DELIMITER ;
CALL UpdateAccount(1, 2, 100);
- 触发器:
CREATE TRIGGER after_account_deposit AFTER INSERT ON transactions
FOR EACH ROW
BEGIN
UPDATE accounts SET balance = balance + NEW.amount WHERE account_id = NEW.account_id;
END;
- 视图:
CREATE VIEW customer_details AS
SELECT customers.customer_id, customers.first_name, customers.last_name, accounts.balance
FROM customers
JOIN accounts ON customers.customer_id = accounts.customer_id;
- 索引优化:
CREATE INDEX idx_customer_last_name ON customers(last_name);
这些例子展示了如何在MySQL中使用高级语句来管理数据库操作。
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