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。
(
a int,
b int
)
begin
declare c int;
set a = 0;
end if;
set b = 0;
end if;
return c;- 不能在 MySQL 存储过程中使用。return 只能出现在函数中。
/
end;
set @b = 20;
创建 MySQL 存储过程的简单语法为:
(
[in|out|inout] 参数 datatype
)
begin
MySQL 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。
(
@a int,- 错误
b int - 正确
)
(
a int,
b int
)
as - 错误,MySQL 不需要 “as”
begin
mysql statement ...;
end;
(
a int,
b int
)
begin
mysql statement 1 ...;
mysql statement 2 ...;
end;
set a = 0;
end if;
这是个
多行 MySQL 注释。
/
set a = 0;
end if;
end;
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“()”
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。
- DELIMITER $$
- DROP PROCEDURE IF EXISTS HelloWorld$$
- CREATE PROCEDURE HelloWorld()
- BEGIN
- SELECT "Hello World!";
- END$$
- DELIMITER ;
3、变量
使用DECLARE来声明,DEFAULT赋默认值,SET赋值
- DECLARE counter INT DEFAULT 0; - 默认为0
- SET counter = counter+1; - 自增+1
4、参数
IN为默认类型,值必须在调用时指定,值不能返回(值传递)
OUT值可以返回(指针传递)
INOUT值必须在调用时指定,值可以返回
eg:
- CREATE PROCEDURE test(a INT, OUT b FLOAT, INOUT c INT)
5、条件判断
eg:
- DELIMITER $$
- DROP PROCEDURE IF EXISTS discounted_price$$
- CREATE PROCEDURE discunted_price(normal_price NUMERIC(8, 2), OUT discount_price NUMERIC(8, 2))
- BEGIN
- IF (normal_price > 500) THEN
- SET discount_price = normal_price * .8;
- ELSEIF (normal_price > 100) THEN
- SET discount_price = normal_price * .9;
- ELSE
- SET discount_price = normal_price;
- END IF;
- END$$
- DELIMITER ;
6、循环
LOOP、END LOOP
eg:
- 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 ;
package com.test; import java.sql.*; public class Test { public static void main(String[] args) throws Exception { String div="com.mysql.jdbc.Driver"; String url="jdbc:mysql://127.0.0.1:3306/mydb?characterEncoding=GBK"; String uid="root"; String pwd=""; Class.forName(div); Connection conn = DriverManager.getConnection(url,uid,pwd); CallableStatement stat = conn.prepareCall("call BBB(?,?)"); stat.setString(1, "k001"); stat.registerOutParameter(2, java.sql.Types.INTEGER); ResultSet rs = stat.executeQuery(); int i =stat.getInt(2); System.out.println(i); while(rs.next()){ System.out.println(rs.getString(2)); } conn.close(); } }
结果为: