DELIMITER $$ DROP PROCEDURE IF EXISTS HelloWorld$$ CREATE PROCEDURE HelloWorld() BEGIN SELECT "Hello World!"; END$$ DELIMITER ;
3,变量 DECLARE声明,SET赋值 可以在DECLARE变量时用DEFAULT设置默认值,不设则为NULL
DECLARE counter INT DEFAULT 0; SET counter = counter+1;
4,参数 IN为默认类型,值必须在调用时指定,值不能返回(值传递) OUT值可以返回(指针传递) INOUT值必须在调用时指定,值可以返回
CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT) CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)
5,条件判断 IF THEN、ELSEIF、ELSE、END IF
代码 DELIMITER $$ DROP PROCEDURE IF EXISTS discounted_price$$ CREATE PROCEDURE discunted_price(normal_price NUMERIC(8, 2), OUT discount_price NUMERIC(8, 2)) BEGIN IF (normal_price > 500) THEN SET discount_price = normal_price * .8; ELSEIF (normal_price > 100) THEN SET discount_price = normal_price * .9; ELSE SET discount_price = normal_price; END IF; END$$ DELIMITER ; 6,循环 LOOP、END LOOP
代码
DELIMITER $$ DROP PROCEDURE IF EXISTS simple_loop$$ CREATE PROCEDURE simple_loop(OUT counter INT) BEGIN SET counter = 0; my_simple_loop: LOOP SET counter = counter+1; IF counter = 10 THEN LEAVE my_simple_loop; END IF; END LOOP my_simple_loop; END$$ DELIMITER ;
WHILE DO、END WHILE
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DELIMITER $$ DROP PROCEDURE IF EXISTS simple_while$$ CREATE PROCEDURE simple_while(OUT counter INT) BEGIN SET counter = 0; WHILE counter != 10 DO SET counter = counter+1; END WHILE; END$$ DELIMITER ;
REPEAT、UNTILL
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DELIMITER $$ DROP PROCEDURE IF EXISTS simple_repeat$$ CREATE PROCEDURE simple_repeat(OUT counter INT) BEGIN SET counter = 0; REPEAT SET counter = counter+1; UNTIL counter = 10 END REPEAT; END$$ DELIMITER ;
7,异常处理 如果用cursor获取SELECT语句返回的所有结果集时应该定义NOT FOUND error handler来防止存储程序提前终结 如果SQL语句可能返回constraint violation等错误时应该创建一个handler来防止程序终结 8,数据库交互 INTO用于存储单行记录的查询结果
DECLARE total_sales NUMERIC(8, 2); SELECT SUM(sale_value) INTO total_sales FROM sales WHERE customer_id=in_customer_id;
CURSOR用于处理多行记录的查询结果
代码
DELIMITER $$ DROP PROCEDURE IF EXITS cursor_example$$ CREATE PROCEDURE cursor_example() READS SQL DATA BEGIN DECLARE l_employee_id INT; DECLARE l_salary NUMERIC(8,2); DECLARE l_department_id INT; DECLARE done INT DEFAULT 0; DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1; OPEN cur1; emp_loop: LOOP FETCH cur1 INTO l_employee_id, l_salary, l_department_id; IF done=1 THEN LEAVE emp_loop; END IF; END LOOP emp_loop; CLOSE cur1; END$$ DELIMITER ;
unbounded SELECT语句用于存储过程返回结果集
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DELIMITER $$ DROP PROCEDURE IF EXISTS sp_emps_in_dept$$ CREATE PROCEDURE sp_emps_in_dept(in_employee_id INT) BEGIN SELECT employee_id, surname, firstname, address1, address2, zipcode, date_of_birth FROM employees WHERE department_id=in_employee_id; END$$ DELIMITER ;
UPDATE、INSERT、DELETE、CREATE TABLE等非查询语句也可以嵌入存储过程里
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DELIMITER $$ DROP PROCEDURE IF EXITS sp_update_salary$$ CREATE PROCEDURE sp_update_salary(in_employee_id INT, in_new_salary NUMERIC(8,2)) BEGIN IF in_new_salary < 5000 OR in_new_salary > 500000 THEN SELECT "Illegal salary: salary must be between $5000 and $500, 000"; ELSE UPDATE employees SET salary=in_new_salary WHERE employee_id=in_employee_id; END IF; END$$ DELIMITER ;
9,使用CALL调用存储程序
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DELIMITER $$ DROP PROCEDURE IF EXISTS call_example$$ CREATE PROCEDURE call_example(employee_id INT, employee_type VARCHAR(20)) NO SQL BEGIN DECLARE l_bonus_amount NUMERIC(8,2); IF employee_type='MANAGER' THEN CALL calc_manager_bonus(employee_id, l_bonus_amount); ELSE CALL calc_minion_bonus(employee_id, l_bonus_amount); END IF; CALL grant_bonus(employee_id, l_bonus_amount); END$$ DELIMITER ;
10,一个复杂的例子
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CREATE PROCEDURE putting_it_all_together(in_department_id INT) MODIFIES SQL DATA BEGIN DECLARE l_employee_id INT; DECLARE l_salary NUMERIC(8,2); DECLARE l_department_id INT; DECLARE l_new_salary NUMERIC(8,2); DECLARE done INT DEFAULT 0; DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees WHERE department_id=in_department_id; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1; CREATE TEMPORARY TABLE IF NOT EXISTS emp_raises (employee_id INT, department_id INT, new_salary NUMERIC(8,2)); OPEN cur1; emp_loop: LOOP FETCH cur1 INTO l_employee_id, l_salary, l_department_id; IF done=1 THEN /* No more rows */ LEAVE emp_loop; END IF; CALL new_salary(1_employee_id, l_new_salary); /* Get new salary */ IF (l_new_salary <> l_salary) THEN /* Salary changed */ UPDATE employees SET salary=l_new_salary WHERE employee_id=l_employee_id; /* Keep track of changed salaries */ INSERT INTO emp_raises(employee_id, department_id, new_salary) VALUES (l_employee_id, l_department_id, l_new_salary); END IF: END LOOP emp_loop; CLOSE cur1; /* Print out the changed salaries */ SELECT employee_id, department_id, new_salary from emp_raises ORDER BY employee_id; END;
11,存储方法 存储方法与存储过程的区别 1,存储方法的参数列表只允许IN类型的参数,而且没必要也不允许指定IN关键字 2,存储方法返回一个单一的值,值的类型在存储方法的头部定义 3,存储方法可以在SQL语句内部调用 4,存储方法不能返回结果集 语法:
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CREATE [DEFINER = { user | CURRENT_USER }] PROCEDURE sp_name ([proc_parameter[,...]]) [characteristic ...] routine_body CREATE [DEFINER = { user | CURRENT_USER }] FUNCTION sp_name ([func_parameter[,...]]) RETURNS type [characteristic ...] routine_body proc_parameter: [ IN | OUT | INOUT ] param_name type func_parameter: param_name type type: Any valid MySQL data type characteristic: LANGUAGE SQL | [NOT] DETERMINISTIC | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA } | SQL SECURITY { DEFINER | INVOKER } | COMMENT 'string' routine_body: Valid SQL procedure statement
各参数说明见CREATE PROCEDURE and CREATE FUNCTION Syntax 例子:
代码
DELIMITER $$ DROP FUNCTION IF EXISTS f_discount_price$$ CREATE FUNCTION f_discount_price (normal_price NUMERIC(8,2)) RETURNS NUMERIC(8,2) DETERMINISTIC BEGIN DECLARE discount_price NUMERIC(8,2); IF (normal_price > 500) THEN SET discount_price = normal_price * .8; ELSEIF (normal_price >100) THEN SET discount_price = normal_price * .9; ELSE SET discount_price = normal_price; END IF; RETURN(discount_price); END$$ DELIMITER ;
12,触发器 触发器在INSERT、UPDATE或DELETE等DML语句修改数据库表时触发 触发器的典型应用场景是重要的业务逻辑、提高性能、监控表的修改等 触发器可以在DML语句执行前或后触发
代码
DELIMITER $$ DROP TRIGGER sales_trigger$$ CREATE TRIGGER sales_trigger BEFORE INSERT ON sales FOR EACH ROW BEGIN IF NEW.sale_value > 500 THEN SET NEW.free_shipping = 'Y'; ELSE SET NEW.free_shipping = 'N'; END IF; IF NEW.sale_value > 1000 THEN SET NEW.discount = NEW.sale_value * .15; ELSE SET NEW.discount = 0; END IF; END$$ DELIMITER ;
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