MYSQL存储过程 注释详解

// 把editUser类比成一个存储过程
public void editUser(User user,String username){
    String a = "nihao";
    user.setUsername(username);
}
main(){
    User user = new User();
 editUser(user,"张三");
    user.getUseranme();   //Java基础
}

delimiter $$ --声明结束符

#### 3.0 语法结构

```sql
-- 存储过程结构
CREATE
    [DEFINER = user]
 PROCEDURE sp_name ([proc_parameter[,...]])
    [characteristic ...] routine_body
    
-- 1. proc_parameter参数部分，可以如下书写：
 [ IN | OUT | INOUT ] param_name type
 -- type类型可以是MySQL支持的所有类型
 
-- 2. routine_body(程序体)部分，可以书写合法的SQL语句 BEGIN ... END

-- 声明结束符。因为MySQL默认使用‘;'作为结束符，而在存储过程中，会使用‘;'作为一段语句的结束，导致‘;'使用冲突
delimiter $$

CREATE PROCEDURE hello_procedure ()
BEGIN
 SELECT 'hello procedure';
END $$

call hello_procedure();

-- set赋值
delimiter $$
create procedure sp_var01()
begin
 declare nickname varchar(32) default 'unkown';
 set nickname = 'ZS';
 -- set nickname := 'SF';
 select nickname;
end$$
-- into赋值
delimiter $$
create procedure sp_var_into()
begin
 declare emp_name varchar(32) default 'unkown' ;
 declare emp_no int default 0;
 select e.empno,e.ename into emp_no,emp_name from emp e where e.empno = 7839;
 select emp_no,emp_name;
end$$

-- 赋值
delimiter $$
create procedure sp_var02()
begin
 set @nickname = 'ZS';
 -- set nickname := 'SF';
end$$
call sp_var02() $$
select @nickname$$  --可以看到结果

show session variables; -- 查看会话变量
select @@session.unique_checks; -- 查看某会话变量
set @@session.unique_checks = 0; --修改会话变量

show global variables like '%char%'; 

-- 查看全局变量character_set_client的值
select @@global.character_set_client; 

-- IN类型演示
delimiter $$
create procedure sp_param01(in age int)
begin
 set @user_age = age;
end$$
call sp_param01(10) $$
select @user_age$$
-- OUT类型，只负责输出！
-- 需求：输出传入的地址字符串对应的部门编号。
delimiter $$

create procedure sp_param02(in loc varchar(64),out dept_no int(11))
begin
 select d.deptno into dept_no from dept d where d.loc = loc;
 --此处强调，要么表起别名，要么入参名不与字段名一致
end$$
delimiter ;

--测试
set @dept_no = 100;
call sp_param02('DALLAS',@dept_no);
select @dept_no;
-- INOUT类型 
delimiter $$
create procedure sp_param03(inout name varchar(49))
begin
 set name = concat('hello' ,name);
end$$
delimiter ;

set @user_name = '小明';
call sp_param03(@user_name);
select @user_name;

-- 语法
IF search_condition THEN statement_list
    [ELSEIF search_condition THEN statement_list] ...
    [ELSE statement_list]
END IF

-- 前置知识点：timestampdiff(unit,exp1,exp2) 取差值exp2-exp1差值，单位是unit
select timestampdiff(year,e.hiredate,now()) from emp e where e.empno = '7499         ';
delimiter $$
-- DROP PROCEDURE IF EXISTS sp_param04;
create procedure sp_param05(in ages timestamp)
begin
 declare result varchar(32);
 if timestampdiff(year,ages,now())>40 
  then set result = '元老';
 elseif timestampdiff(year,ages,now())>38 
  then set result = '老员工';
 ELSE 
  SET result = '新手';
 end if;
 select result;
end $$
delimiter;
 
call sp_param05('1970-02-26 10:00:25');
-- 注意：MYSQL时间戳必须从1970年开始。

-- 语法一（类比java的switch）：
CASE case_value
    WHEN when_value THEN statement_list
    [WHEN when_value THEN statement_list] ...
    [ELSE statement_list]
END CASE
-- 语法二：
CASE
    WHEN search_condition THEN statement_list
    [WHEN search_condition THEN statement_list] ...
    [ELSE statement_list]
END CASE

-- 需求：入职年限年龄<=38是新手 >38并 <=40老员工 >40元老
delimiter $$
create procedure sp_hire_case()
begin
 declare result varchar(32);
 declare message varchar(64);
 case
    when timestampdiff(year,'2001-01-01',now()) > 40 
  then 
   set result = '元老';
   set message = '老爷爷';
 when timestampdiff(year,'2001-01-01',now()) > 38
  then 
   set result = '老员工';
   set message = '油腻中年人';
 else 
  set result = '新手';
  set message = '萌新';
 end case;
 select result;
end$$
delimiter ;

-- 语法
[begin_label:] LOOP
    statement_list
END LOOP [end_label]

--需求：循环打印1到10
-- leave控制循环的退出
delimiter $$
create procedure sp_flow_loop()
begin
 declare c_index int default 1;
 declare result_str  varchar(256) default '1';
 cnt:loop
 
  if c_index >= 10
  then leave cnt;
  end if;

  set c_index = c_index + 1;
  set result_str = concat(result_str,',',c_index);
  
 end loop cnt;
 
 select result_str;
end$$

-- iterate + leave控制循环
delimiter $$
create procedure sp_flow_loop02()
begin
 declare c_index int default 1;
 declare result_str  varchar(256) default '1';
 cnt:loop

  set c_index = c_index + 1;
  set result_str = concat(result_str,',',c_index);
  if c_index < 10 then 
   iterate cnt; 
  end if;
  -- 下面这句话能否执行到？什么时候执行到？ 当c_index < 10为false时执行
  leave cnt;
  
 end loop cnt;
 select result_str;
 
end$$

[begin_label:] REPEAT
    statement_list
UNTIL search_condition -- 直到…为止，才退出循环
END REPEAT [end_label]
-- 需求：循环打印1到10
delimiter $$
create procedure sp_flow_repeat()
begin
 declare c_index int default 1;
 -- 收集结果字符串
 declare result_str varchar(256) default '1';
 count_lab:repeat
  set c_index = c_index + 1;
  set result_str = concat(result_str,',',c_index);
  until c_index >= 10
 end repeat count_lab;
 select result_str;
end$$

类比java的while(){}
[begin_label:] WHILE search_condition DO
    statement_list
END WHILE [end_label]
-- 需求：循环打印1到10
delimiter $$
create procedure sp_flow_while()
begin
 declare c_index int default 1;
 -- 收集结果字符串
 declare result_str varchar(256) default '1';
 while c_index < 10 do
  set c_index = c_index + 1;
  set result_str = concat(result_str,',',c_index);
 end while;
 select result_str;
end$$

类比java的breake
-- 退出 LEAVE can be used within BEGIN ... END or loop constructs (LOOP, REPEAT, WHILE).
LEAVE label

类比java的continue
-- 继续循环 ITERATE can appear only within LOOP, REPEAT, and WHILE statements
ITERATE label

类比jdbc的ResultSet
-- 声明语法
DECLARE cursor_name CURSOR FOR select_statement
-- 打开语法
OPEN cursor_name
-- 取值语法
FETCH cursor_name INTO var_name [, var_name] ...
-- 关闭语法
CLOSE cursor_name
-- 需求：按照部门名称查询员工，通过select查看员工的编号、姓名、薪资。（注意，此处仅仅演示游标用法）
-- 更改结束符为$$
delimiter $$
-- 创造存储过程(带一个入参)
create procedure sp_create_table02(in dept_name varchar(32))
begin
-- 必须先声明变量
 declare e_no int;
 declare e_name varchar(32);
 declare e_sal decimal(7,2);
 
 declare lp_flag boolean default true;
-- 其次声明游标:游标值为query（dept_name)得到的table(e.empno,e.ename,e.sal)
 declare emp_cursor cursor for 
  select e.empno,e.ename,e.sal
  from emp e,dept d
  where e.deptno = d.deptno and d.dname = dept_name;
  
-- 然后声明 handler 句柄：
-- 关于句柄:https://blog.csdn.net/qq_43427482/article/details/109898934
-- 看完还没理解，再看：https://www.cnblogs.com/PHPper/p/7587556.html
-- 这里涉及了SQL STATE:https://blog.csdn.net/u014653854/article/details/78986780
-- 声明handler句柄:当每条SQL传递ERROR STATE为没有值的报错时，设定变量lp_flag为非真，同时继续执行SQL（如不声明，当某条循环报错时，整个SQL将直接停止循环）
 declare continue handler for NOT FOUND set lp_flag = false;
-- 打开游标
 open emp_cursor;
-- 开启LOOP循环：emp_loop
 emp_loop:loop
-- 将游标值传递给三个变量
  fetch emp_cursor into e_no,e_name,e_sal;
-- 如果变量lp_flag为真，则获取这三个参数的值；否则打断emp_loop循环
  if lp_flag then
   select e_no,e_name,e_sal;
  else
   leave emp_loop;
  end if;
-- 结束循环
 end loop emp_loop;
-- 定义用户变量并赋值（用户变量不需要提前声明、仅当前会话有效）>鄙人没有理解这一步什么意义
 set @end_falg = 'exit_flag';
-- 关闭游标
 close emp_cursor;
-- 结束存储过程
end$$
-- 恢复;结束符
delimiter;

-- 使用该存储过程并传参
call sp_create_table02('RESEARCH');

DECLARE handler_action HANDLER
    FOR condition_value [, condition_value] ...
    statement

handler_action: {
    CONTINUE  -- 继续执行
  | EXIT      -- 退出执行
  | UNDO      -- 什么都不做
}

CONTINUE: Execution of the current program continues. -- 继续执行当前程序
EXIT: Execution terminates for the BEGIN ... END compound statement in which the handler is declared. This is true even if the condition occurs in an inner block. -- 停止执行在handler被声明的BEGIN... END的组合程序，即使是在程序内部发生该条件。

condition_value: {
    mysql_error_code
  | SQLSTATE [VALUE] sqlstate_value
  | condition_name
  | SQLWARNING
  | NOT FOUND
  | SQLEXCEPTION
}

SQLWARNING: Shorthand for the class of SQLSTATE values that begin with '01'. -- 即SQL STATE以01开头的集合代称
NOT FOUND: Shorthand for the class of SQLSTATE values that begin with '02'. -- 即SQL STATE以O2开头的集合代称
SQLEXCEPTION: Shorthand for the class of SQLSTATE values that do not begin with '00', '01', or '02'. -- 即SQL STATE不以00、01、02开头的集合代称
-- 各种写法：
 DECLARE exit HANDLER FOR SQLSTATE '42S01' set @res_table = 'EXISTS';
 DECLARE continue HANDLER FOR 1050 set @res_table = 'EXISTS';
 DECLARE continue HANDLER FOR not found set @res_table = 'EXISTS';

delimiter // -- 定义结束符
create procedure high_sal(in dept_name varchar(32)) -- 创建存储过程
begin -- 开始存储过程
 declare e_no int; -- 声明变量
 declare e_name varchar(32);
 declare e_sal decimal(7,2);
 
 declare lp_flag boolean default true;
 
 declare emp_cursor cursor for  -- 声明游标
  select e.empno,e.ename,e.sal
  from emp e,dept d
  where e.deptno = d.deptno and d.dname = dept_name;
  
 -- 声明handler句柄（条件处理）
 declare continue handler for NOT FOUND set lp_flag = false;
  
 open emp_cursor; -- 打开游标
 
 emp_loop:loop -- 开启循环
  fetch emp_cursor into e_no,e_name,e_sal; -- 变量赋值
  
  if lp_flag then -- 流程控制
   if e_name = 'king' then 
    iterate emp_loop; -- 继续循环
   else 
    update emp e set e.sal = e.sal + 100 where e.empno = e_no; -- 更新数据
   end if;
  else
   leave emp_loop; -- 离开循环
  end if; -- 结束流程
  
 end loop emp_loop; -- 结束循环
 set @end_falg = 'exit_flag'; -- 声明用户变量
 close emp_cursor; -- 变比游标
end // -- 结束存储过程
delimiter; -- 恢复结束符


call high_sal('ACCOUNTING');

-- 知识点 预处理 prepare语句from后使用局部变量会报错 
-- https://dev.mysql.com/doc/refman/5.6/en/sql-prepared-statements.html
-- 看不懂英文文档的看这个：https://www.cnblogs.com/geaozhang/p/9891338.html；话说我也该去做一点英文技术文档的阅读提升了
PREPARE stmt_name FROM preparable_stmt
EXECUTE stmt_name [USING @var_name [, @var_name] ...]
{DEALLOCATE | DROP} PREPARE stmt_name

-- 贴一段预处理的案例，需求是：利用字符串定义预处理 SQL (直角三角形斜边hypotenuse计算)
PREPARE stmt1 FROM 'SELECT SQRT(POW(?,2) + POW(?,2)) AS hypotenuse'; -- POW(x,y)函数,用于计算x的y次方（http://c.biancheng.net/mysql/pow_power.html）；SQRT函数用于求平方根（https://blog.csdn.net/weixin_39554172/article/details/113124290）
SET @a = 3;
SET @b = 4;  -- 用户变量使用即声明
EXECUTE stmt1 USING @a, @b; -- 结果为5
DEALLOCATE PREPARE stmt1; 

-- 知识点 时间的处理
-- EXTRACT(unit FROM date)截取时间的指定位置值
-- DATE_ADD(date,INTERVAL expr unit)  日期运算
-- LAST_DAY(date)  获取日期的最后一天的日期
-- YEAR(date) 返回日期中的年
-- MONTH(date) 返回日期的月
-- DAYOFMONTH(date) 返回日 -- 注：根据https://stackoverflow.com/questions/35838321/day-vs-dayofmonth-in-mysql，其实DAY(date)效果是一样的
-- 思路：循环构建表名 comp_2020_05_01 到 comp_2020_05_31；并执行create语句。
-- 分析：1. 循环构筑表，仅表名不同，考虑使用存储过程执行循环处理、使用预处理提高效率。 2. 首先需要一个变量存储执行SQL；然后年份需要一个变量、月份需要一个变量、日期需要一个变量、拼接出来的表名需要一个变量；除此之外，还需要一个数字用来累增；至此，我们得到了至少需要6个变量。为了补全日期0，增加两个月份、日的变量用来补充0形成01、02···。 3. 考虑到预处的格式（from后不能有局部变量）,写7个局部变量，1个用户变量
delimiter //  --声明结束符
create procedure sp_create_table()
begin
--  定义一堆局部变量
 declare next_year int;
 declare next_month int;
 declare next_month_maxday int;
  
 declare next_month_str char(2);
 declare next_month_maxday_str char(2);
 
 -- 处理每天的表名
 declare table_name_str char(10);
 -- 统计序列
 declare t_index int default 1;
 -- declare create_table_sql varchar(200);
 
 -- 获取下个月的年份
 set next_year = year(date_add(now(),INTERVAL 1 month));
 -- 获取下个月是几月 
 set next_month = month(date_add(now(),INTERVAL 1 month));
 -- 下个月最后一天是几号
 set next_month_maxday = dayofmonth(LAST_DAY(date_add(now(),INTERVAL 1 month)));
 
 -- 把1-9月补上0:  01,02····，09
 if next_month < 10
  then set next_month_str = concat('0',next_month);
 else
  set next_month_str = concat('',next_month);
 end if;
 
 
 while t_index <= next_month_maxday do
  
  -- 同上，对天数补0
  if (t_index < 10)
   then set next_month_maxday_str = concat('0',t_index);
  else
   set next_month_maxday_str = concat('',t_index);
  end if;
  
  -- 2020_05_01
  set table_name_str = concat(next_year,'_',next_month_str,'_',next_month_maxday_str);
  -- 拼接create sql语句（用户变量）
  set @create_table_sql = concat(
     'create table comp_',
     table_name_str,
     '(`grade` INT(11) NULL,`losal` INT(11) NULL,`hisal` INT(11) NULL) COLLATE=\'utf8_general_ci\' ENGINE=InnoDB');
  -- FROM后面不能使用局部变量！这就是我们为什么使用用户变量的原因
  prepare create_table_stmt FROM @create_table_sql;
  execute create_table_stmt;
  DEALLOCATE prepare create_table_stmt;
  
  set t_index = t_index + 1;
  
 end while; 
end//
delimiter;

call sp_create_table()

-- 以下为个人精简版

delimiter //
CREATE PROCEDURE sp_createtable1 () BEGIN-- 统计序列
 DECLARE
  t_index INT DEFAULT 1;
 WHILE
   t_index <= DAY (
    LAST_DAY(
    date_add( now(), INTERVAL 1 MONTH ))) DO
   
   SET @create_table_sql = concat(
    'CREATE TABLE comp_',
    YEAR (
    date_add( now(), INTERVAL 1 MONTH )),
    '_',
    MONTH (
    date_add( now(), INTERVAL 1 MONTH )),
    '_',
    t_index,
    '(`grade` INT(11) NULL,`losal` INT(11) NULL,`hisal` INT(11) NULL) COLLATE=\'utf8_general_ci\' ENGINE=InnoDB' 
   );-- FROM后面不能使用局部变量！这就是我们为什么使用用户变量的原因
  PREPARE create_table_stmt 
  FROM
   @create_table_sql;
  EXECUTE create_table_stmt;
  DEALLOCATE PREPARE create_table_stmt;
  
  SET t_index = t_index + 1;
  
 END WHILE;
 
END // 
delimiter;
CALL sp_createtable1 ()

characteristic:
    COMMENT 'string'
  | LANGUAGE SQL
  | [NOT] DETERMINISTIC
  | { CONTAINS SQL | NO SQL | READS SQL DATA | MODIFIES SQL DATA }
  | SQL SECURITY { DEFINER | INVOKER }

-- 如有死循环处理，可以通过下面的命令查看并结束
show processlist;
kill id;

https://dev.mysql.com/doc/refman/5.6/en/control-flow-functions.html
select 
 case
  when timestampdiff(year,e.hiredate,now()) <= 38 then '新手'
  when timestampdiff(year,e.hiredate,now()) <= 40 then '老员工'
  else '元老'
 end hir_loc,
 e.*
from emp e;

create temporary table 表名(
　　字段名 类型 [约束],
　　name varchar(20) 
)Engine=InnoDB default charset utf8;

-- 需求：按照部门名称查询员工，通过select查看员工的编号、姓名、薪资。（注意，此处仅仅演示游标用法）
delimiter $$
create procedure sp_create_table02(in dept_name varchar(32))
begin
 declare emp_no int;
 declare emp_name varchar(32);
 declare emp_sal decimal(7,2);
 declare exit_flag int default 0;
 
 declare emp_cursor cursor for
  select e.empno,e.ename,e.sal
  from emp e inner join dept d on e.deptno = d.deptno where d.dname = dept_name;
 
 declare continue handler for not found set exit_flag = 1;
 
 -- 创建临时表收集数据
 CREATE temporary TABLE `temp_table_emp` (
  `empno` INT(11) NOT NULL COMMENT '员工编号',
  `ename` VARCHAR(32) NULL COMMENT '员工姓名' COLLATE 'utf8_general_ci',
  `sal` DECIMAL(7,2) NOT NULL DEFAULT '0.00' COMMENT '薪资',
  PRIMARY KEY (`empno`) USING BTREE
 )
 COLLATE='utf8_general_ci'
 ENGINE=InnoDB; 
 
 open emp_cursor;
 
 c_loop:loop
  fetch emp_cursor into emp_no,emp_name,emp_sal;
  
  
  if exit_flag != 1 then
   insert into temp_table_emp values(emp_no,emp_name,emp_sal); 
  else
   leave c_loop;
  end if;
  
 end loop c_loop;
 
 select * from temp_table_emp;
 
 select @sex_res; -- 仅仅是看一下会不会执行到
 close emp_cursor;
 
end$$

call sp_create_table02('RESEARCH');

CREATE TABLE `dept` (
 `deptno` INT(11) NOT NULL COMMENT '部门编号',
 `dname` VARCHAR(32) NULL COMMENT '部门名称' COLLATE 'utf8_general_ci',
 `loc` VARCHAR(64) NULL COMMENT '部门地址' COLLATE 'utf8_general_ci',
 PRIMARY KEY (`deptno`) USING BTREE
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
;
INSERT INTO DEPT VALUES
 (10,'ACCOUNTING','NEW YORK');
INSERT INTO DEPT VALUES (20,'RESEARCH','DALLAS');
INSERT INTO DEPT VALUES
 (30,'SALES','CHICAGo');
INSERT INTO DEPT VALUES
 (40,'OPERATIONS','BOSTON');
 
CREATE TABLE `emp` (
 `empno` INT(11) NOT NULL COMMENT '员工编号',
 `ename` VARCHAR(32) NULL COMMENT '员工姓名' COLLATE 'utf8_general_ci',
 `job` VARCHAR(10) NULL COMMENT '职位' COLLATE 'utf8_general_ci',
 `mgr` INT(11) NULL COMMENT '上级编号',
 `hiredate` DATE NOT NULL COMMENT '入职时间',
 `sal` DECIMAL(7,2) NOT NULL DEFAULT '0.00' COMMENT '薪资',
 `comm` DECIMAL(7,2) NULL COMMENT '年终奖金',
 `deptno` INT(11) NOT NULL COMMENT '部门编号',
 PRIMARY KEY (`empno`) USING BTREE,
 INDEX `FK_emp_dept` (`deptno`) USING BTREE,
 CONSTRAINT `FK_emp_dept` FOREIGN KEY (`deptno`) REFERENCES `procedure_demo`.`dept` (`deptno`) ON UPDATE RESTRICT ON DELETE RESTRICT
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
;

insert into emp values
(7369,'smith','clerk',7902,'1980-12-17',800,null,20);
insert into emp values
(7499,'allen','salesman',7698,'1981-02-20',1600,300,30);
insert into emp values
(7521,'ward','salesman',7698,'1981-02-22',1250,500,30);
insert into emp values
(7566,'jones','manager',7839,'1981-02-04',2975,null,20);
insert into emp values
(7654,'martin','salesman',7698,'1981-09-28',1250,1400,30);
insert into emp values
(7698,'blake','manager',7839,'1981-05-01',2850,null,30);
insert into emp values
(7782,'clark','manager',7839,'1981-06-09',2450,null,10);
insert into emp values
(7788,'scott','analyst',7566,'1987-07-13')-85,3000,null,20);
insert into emp values
(7839,'king','president',null,'1981-11-17',5000,null,10);
insert into emp values
(7844,'turner','salesman',7698,'1981-09-08',1500,0,30);
insert into emp values
(7876,'adams','clerk',7788,'1987-07-13')-51,1100,null,20);
insert into emp values
(7900,'james','clerk',7698,'1981-12-03',950,null,30);
insert into emp values
(7902,'ford','analyst',7566,'1981-12-03',3000,null,20);
insert into emp values
(7934,'miller','clerk',7782,'1982-01-23',1300,null,10);

CREATE TABLE `salgrade` (
 `grade` INT(11) NULL,
 `losal` INT(11) NULL,
 `hisal` INT(11) NULL
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
;
insert into salgrade values (1,700,1200);
insert into salgrade values (2,1201,1400);
insert into salgrade values (3,1401,2000);
insert into salgrade values (4,2001,3000);
insert into salgrade values (5,3001,9999);