mysql存储过程 基本语法

话不多说一、MySQL 创建存储过程“pr_add” 是个简单的 MySQL 存储过程，这个存储过程有两个 int 类型的输入参数 “a”、“b”，返回这两个参数的和。drop procedure if exists pr_add;-- 计算两个数之和create procedure pr_add(a int,b int)begindeclare c int;if a is null thenset a = 0;end if;if b is null thenset b = 0;end if;set c = a + b;select c as sum;/*return c;- 不能在 MySQL 存储过程中使用。return 只能出现在函数中。/end;二、调用Mysql存储过程eg： call pr_add(10,20);执行 MySQL 存储过程，存储过程参数为 MySQL 用户变量。set @a = 10;set @b = 20;call pr_add(@a, @b);三、MySQL 存储过程特点创建 MySQL 存储过程的简单语法为：create procedure 存储过程名字()([in|out|inout] 参数 datatype)beginMySQL 语句;end;MySQL 存储过程参数如果不显式指定“in”、“out”、“inout”，则默认为“in”。习惯上，对于是“in” 的参数，我们都不会显式指定。如下，给出解释1. MySQL 存储过程名字后面的“()”是必须的，即使没有一个参数，也需要“()”2. MySQL 存储过程参数，不能在参数名称前加“@”，如：“@a int”。下面的创建存储过程语法在 MySQL 中是错误的（在 SQL Server 中是正确的）。 MySQL 存储过程中的变量，不需要在变量名字前加“@”，虽然 MySQL 客户端用户变量要加个“@”。create procedure pr_add(@a int,- 错误b int - 正确)3. MySQL 存储过程的参数不能指定默认值。4. MySQL 存储过程不需要在 procedure body 前面加 “as”。而 SQL Server 存储过程必须加 “as” 关键字。create procedure pr_add(a int,b int)as - 错误，MySQL 不需要 “as”beginmysql statement ...;end;5. 如果 MySQL 存储过程中包含单条或者多条 MySQL 语句，都需要 begin end 关键字。create procedure pr_add(a int,b int)beginmysql statement 1 ...;mysql statement 2 ...;end;6.MySQL 存储过程中的每条语句的末尾，都要加上分号 “;”...declare c int;if a is null thenset a = 0;end if;...7. MySQL 存储过程中的注释。/*这是个多行 MySQL 注释。/declare c int; - 这是单行 MySQL 注释 （注意- 后至少要有一个空格）if a is null then 这也是个单行 MySQL 注释set a = 0;end if;...end;8. 不能在 MySQL 存储过程中使用 “return” 关键字。set c = a + b;select c as sum;/*return c;- 不能在 MySQL 存储过程中使用。return 只能出现在函数中。/end;9. 调用 MySQL 存储过程时候，需要在过程名字后面加“()”，即使没有一个参数，也需要“()”call pr_no_param();10. 因为 MySQL 存储过程参数没有默认值，所以在调用 MySQL 存储过程时候，不能省略参数。可以用 null 来替代。call pr_add(10, null);1、当然以上这些，前提是 mysql 52、下面写一个mysql存储过程之 Hello WorldDELIMITER $$DROP PROCEDURE IF EXISTS HelloWorld$$CREATE PROCEDURE HelloWorld()BEGINSELECT "Hello World!";END$$DELIMITER ;3、变量使用DECLARE来声明，DEFAULT赋默认值，SET赋值DECLARE counter INT DEFAULT 0; - 默认为0SET counter = counter+1; - 自增+14、参数IN为默认类型，值必须在调用时指定，值不能返回（值传递）OUT值可以返回（指针传递）INOUT值必须在调用时指定，值可以返回eg:CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)5、条件判断eg:DELIMITER $$DROP PROCEDURE IF EXISTS discounted_price$$CREATE PROCEDURE discunted_price(normal_price NUMERIC(8, 2), OUT discount_price NUMERIC(8, 2))BEGINIF (normal_price > 500) THENSET discount_price = normal_price * .8;ELSEIF (normal_price > 100) THENSET discount_price = normal_price * .9;ELSESET discount_price = normal_price;END IF;END$$DELIMITER ;6、循环LOOP、END LOOPeg:DELIMITER $$DROP PROCEDURE IF EXISTS simple_loop$$CREATE PROCEDURE simple_loop(OUT counter INT)BEGINSET counter = 0;my_simple_loop: LOOPSET counter = counter+1;IF counter = 10 THENLEAVE my_simple_loop;END IF;END LOOP my_simple_loop;END$$DELIMITER ;WHILE DO、END WHILEDELIMITER $$DROP PROCEDURE IF EXISTS simple_while$$CREATE PROCEDURE simple_while(OUT counter INT)BEGINSET counter = 0;WHILE counter != 10 DOSET counter = counter+1;END WHILE;END$$DELIMITER ;REPEAT、UNTILLDELIMITER $$DROP PROCEDURE IF EXISTS simple_repeat$$CREATE PROCEDURE simple_repeat(OUT counter INT)BEGINSET counter = 0;REPEATSET 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$$CREATE PROCEDURE cursor_example()READS SQL DATABEGINDECLARE l_employee_id INT;DECLARE l_salary NUMERIC(8,2);DECLARE l_department_id INT;DECLARE done INT DEFAULT 0;DECLARE cur1 CURSOR FOR SELECT employee_id, salary, department_id FROM employees;DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;OPEN cur1;emp_loop: LOOPFETCH cur1 INTO l_employee_id, l_salary, l_department_id;IF done=1 THENLEAVE emp_loop;END IF;END LOOP emp_loop;CLOSE cur1;END$$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)BEGINSELECT 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$$CREATE PROCEDURE sp_update_salary(in_employee_id INT, in_new_salary NUMERIC(8,2))BEGINIF in_new_salary < 5000 OR in_new_salary > 500000 THENSELECT "Illegal salary: salary must be between $5000 and $500, 000";ELSEUPDATE employees SET salary=in_new_salary WHERE employee_id=in_employee_id;END IF:END$$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 SQLBEGINDECLARE l_bonus_amount NUMERIC(8,2);IF employee_type='MANAGER' THENCALL calc_manager_bonus(employee_id, l_bonus_amount);ELSECALL calc_minion_bonus(employee_id, l_bonus_amount);END IF;CALL grant_bonus(employee_id, l_bonus_amount);END$$DELIMITER ;10，一个复杂的例子CREATE PROCEDURE putting_it_all_together(in_department_id INT)MODIFIES SQL DATABEGINDECLARE l_employee_id INT;DECLARE l_salary NUMERIC(8,2);DECLARE l_department_id INT;DECLARE l_new_salary NUMERIC(8,2);DECLARE done INT DEFAULT 0;DECLARE cur1 CURSOR FORSELECT employee_id, salary, department_idFROM employeesWHERE department_id=in_department_id;DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;CREATE TEMPORARY TABLE IF NOT EXISTS emp_raises(employee_id INT, department_id INT, new_salary NUMERIC(8,2));OPEN cur1;emp_loop: LOOPFETCH cur1 INTO l_employee_id, l_salary, l_department_id;IF done=1 THEN /* No more rows */LEAVE emp_loop;END IF;CALL new_salary(1_employee_id, l_new_salary); /* Get new salary */IF (l_new_salary <> l_salary) THEN /* Salary changed */UPDATE employeesSET salary=l_new_salaryWHERE employee_id=l_employee_id;/* Keep track of changed salaries */INSERT INTO emp_raises(employee_id, department_id, new_salary)VALUES (l_employee_id, l_department_id, l_new_salary);END IF:END LOOP emp_loop;CLOSE cur1;/* Print out the changed salaries */SELECT employee_id, department_id, new_salary from emp_raisesORDER BY employee_id;END;11，存储方法存储方法与存储过程的区别1，存储方法的参数列表只允许IN类型的参数，而且没必要也不允许指定IN关键字2，存储方法返回一个单一的值，值的类型在存储方法的头部定义3，存储方法可以在SQL语句内部调用4，存储方法不能返回结果集语法：CREATE[DEFINER = { user | CURRENT_USER }]PROCEDURE sp_name ([proc_parameter[,...]])[characteristic ...] routine_bodyCREATE[DEFINER = { user | CURRENT_USER }]FUNCTION sp_name ([func_parameter[,...]])RETURNS type[characteristic ...] routine_bodyproc_parameter:[ IN | OUT | INOUT ] param_name typefunc_parameter:param_name typetype:Any valid MySQL data typecharacteristic:LANGUAGE SQL| [NOT] DETERMINISTIC| { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }| SQL SECURITY { DEFINER | INVOKER }| COMMENT 'string'routine_body:Valid SQL procedure statement各参数说明见CREATE PROCEDURE and CREATE FUNCTION Syntax例子：DELIMITER $$DROP FUNCTION IF EXISTS f_discount_price$$CREATE FUNCTION f_discount_price(normal_price NUMERIC(8,2))RETURNS NUMERIC(8,2)DETERMINISTICBEGINDECLARE discount_price NUMERIC(8,2);IF (normal_price > 500) THENSET discount_price = normal_price * .8;ELSEIF (normal_price >100) THENSET discount_price = normal_price * .9;ELSESET discount_price = normal_price;END IF;RETURN(discount_price);END$$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_triggerBEFORE INSERT ON salesFOR EACH ROWBEGINIF NEW.sale_value > 500 THENSET NEW.free_shipping = 'Y';ELSESET NEW.free_shipping = 'N';END IF;IF NEW.sale_value > 1000 THENSET NEW.discount = NEW.sale_value * .15;ELSESET NEW.discount = 0;END IF;END$$DELIMITER ;