MySQL存储过程

来源：互联网发布：php引号转义编辑：程序博客网时间：2024/06/04 22:44

DELIMITER $$     DROP PROCEDURE IF EXISTS HelloWorld$$   CREATE PROCEDURE HelloWorld()   BEGIN        SELECT "Hello World!";   END$$   DELIMITER ;     　　3，变量　　DECLARE声明，SET赋值可以在DECLARE变量时用DEFAULT设置默认值，不设则为NULL DECLARE counter INT DEFAULT 0;   SET counter = counter+1;     　 4，参数IN为默认类型，值必须在调用时指定，值不能返回（值传递）OUT值可以返回（指针传递）INOUT值必须在调用时指定，值可以返回 CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)   CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT) 　  5，条件判断--IF THEN、ELSEIF、ELSE、END IFDELIMITER $$   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  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$$     DELIMITER ;    --WHILE DO、END WHILE DELIMITER $$     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 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

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

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

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

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

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：

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：

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

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 ;

0 0