Mysql-通过创建存储过程完成“对多个同类表进行查询并将结果汇总储存在新表中”

案例背景：公司数据储存在N张表中，N是大数，现在需要求每个类别某类数据topN用户的数据
代码结果：创建存储过程将数据从多个相同表中查询求topN并存入，

本文主要内容

知识点

分组查询topN问题 https://editor.csdn.net/md/?articleId=126635132

创建存储过程

案例

存储过程知识点介绍

mysql存储过程文档：
https://www.runoob.com/w3cnote/mysql-stored-procedure.html

案例
建立数据集

#创建表
create table orders1 (
    orderid int(11) not null primary key ,
    Itemid varchar(30) not null ,
    category varchar(10) not null ,
    orderdate datetime not null ,
    sales float not null );#创建表
create table orders2 like orders1;
create table orders3 like orders1;
create table orders4 like orders1;
create table orders5 like orders1;
#插入数据
insert into orders1 (orderid, Itemid, category, orderdate, sales)
values ('1','k1','A','2020-1-2','459.5'),
       ('2','k2','A','2020-2-2','345.4'),
       ('3','k1','A','2020-1-7','47'),
       ('4','k3','C','2020-1-21','678'),
       ('5','k4','B','2020-5-2','345'),
       ('6','k5','C','2020-3-12','654'),
       ('7','k4','B','2020-4-25','464'),
       ('8','k2','A','2020-5-28','632'),
       ('9','k3','C','2020-7-20','98'),
       ('10','k5','C','2020-4-28','455.6'),
         ('11','k1','A','2020-3-27','459.7'),
       ('12','k2','A','2020-2-23','776.6'),
       ('13','k4','B','2020-2-12','759'),
       ('14','k5','C','2020-8-2','999'),
       ('15','k2','A','2020-9-21','599'),
       ('16','k3','C','2020-10-21','433'),
       ('17','k4','B','2020-10-28','232'),
       ('18','k5','C','2020-10-3','124'),
       ('19','k3','C','2020-6-6','321.4'),
       ('20','k4','B','2020-9-11','788.6');
 insert into orders2 (orderid, Itemid, category, orderdate, sales)
values ('21','k1','A','2020-1-3','954.5'),
       ('22','k2','A','2020-2-4','435.4'),
       ('23','k1','A','2020-1-8','74'),
       ('24','k3','C','2020-7-5','78'),
       ('25','k4','B','2020-5-26','35'),
       ('26','k5','C','2020-3-10','54'),
       ('27','k4','B','2020-4-29','44'),
       ('28','k2','A','2020-5-24','32'),
       ('29','k3','C','2020-7-7','98'),
       ('30','k5','C','2020-4-6','45.6'),
         ('31','k1','A','2020-3-23','49.7'),
       ('32','k2','A','2020-2-1','76.6'),
       ('33','k4','B','2020-2-18','759'),
       ('34','k5','C','2020-8-29','99'),
       ('35','k2','A','2020-9-29','59'),
       ('36','k3','C','2020-10-25','43'),
       ('37','k4','B','2020-10-28','22'),
       ('38','k5','C','2020-10-3','14'),
       ('39','k3','C','2020-6-10','31.4'),
       ('40','k4','B','2020-9-11','78.6');
insert into orders3 (orderid, Itemid, category, orderdate, sales)
values ('41','k1','A','2020-1-3','954.5'),
       ('42','k2','A','2020-2-4','435.4'),
       ('43','k1','A','2020-1-8','674'),
       ('44','k3','C','2020-7-5','478'),
       ('45','k4','B','2020-5-26','635'),
       ('46','k5','C','2020-3-10','654'),
       ('47','k4','B','2020-4-29','644'),
       ('48','k2','A','2020-5-24','632'),
       ('49','k3','C','2020-7-7','98'),
       ('50','k5','C','2020-4-6','645.6'),
         ('51','k1','A','2020-3-23','49.7'),
       ('52','k2','A','2020-2-1','676.6'),
       ('53','k4','B','2020-2-18','759'),
       ('54','k5','C','2020-8-29','99'),
       ('55','k2','A','2020-9-29','459'),
       ('56','k3','C','2020-10-25','443'),
       ('57','k4','B','2020-10-28','522'),
       ('58','k5','C','2020-10-3','614'),
       ('59','k3','C','2020-6-10','31.4'),
       ('60','k4','B','2020-9-11','78.6');
insert into orders4 (orderid, Itemid, category, orderdate, sales)
values ('61','k1','A','2020-1-3','954.5'),
       ('62','k2','A','2020-2-4','4435.4'),
       ('63','k1','A','2020-1-8','874'),
       ('64','k3','C','2020-7-5','778'),
       ('65','k4','B','2020-5-26','535'),
       ('66','k5','C','2020-3-10','754'),
       ('67','k4','B','2020-4-29','644'),
       ('68','k2','A','2020-5-24','932'),
       ('69','k3','C','2020-7-7','898'),
       ('70','k5','C','2020-4-6','645.6'),
         ('71','k1','A','2020-3-23','449.7'),
       ('72','k2','A','2020-2-1','376.6'),
       ('73','k4','B','2020-2-18','759'),
       ('74','k5','C','2020-8-29','399'),
       ('75','k2','A','2020-9-29','159'),
       ('76','k3','C','2020-10-25','343'),
       ('77','k4','B','2020-10-28','222'),
       ('78','k5','C','2020-10-3','114'),
       ('79','k3','C','2020-6-10','231.4'),
       ('80','k4','B','2020-9-11','178.6');
insert into orders5 (orderid, Itemid, category, orderdate, sales)
values ('81','k1','A','2020-1-3','1954.5'),
       ('82','k2','A','2020-2-4','1435.4'),
       ('83','k1','A','2020-1-8','174'),
       ('84','k3','C','2020-7-5','178'),
       ('85','k4','B','2020-5-26','35'),
       ('86','k5','C','2020-3-10','154'),
       ('87','k4','B','2020-4-29','144'),
       ('88','k2','A','2020-5-24','132'),
       ('89','k3','C','2020-7-7','198'),
       ('90','k5','C','2020-4-6','145.6'),
         ('91','k1','A','2020-3-23','149.7'),
       ('92','k2','A','2020-2-1','176.6'),
       ('93','k4','B','2020-2-18','1759'),
       ('94','k5','C','2020-8-29','199'),
       ('95','k2','A','2020-9-29','159'),
       ('96','k3','C','2020-10-25','143'),
       ('97','k4','B','2020-10-28','122'),
       ('98','k5','C','2020-10-3','114'),
       ('99','k3','C','2020-6-10','131.4'),
       ('100','k4','B','2020-9-11','178.6');
 

创建存储过程
创建一个表data来储存查询结果数据集

create table data (category varchar(10) not null ,orderid int(11) not null primary key ,
    Itemid varchar(30) not null ,
    sales float not null
);

#如果你需要调试存储过程一定要加这句代码
drop procedure if exists insert_odata;

存储过程主体

delimiter ;;
create procedure insert_odata (IN i int)
begin
    DECLARE i int;
    set i=1;
    while i<=5 do
          set @sqlStr:=CONCAT('insert into data (select category, orderid,Itemid,sales from(
select category,orderid,Itemid,sales,
           row_number()over(partition by category order by category,sales desc ) as ranking
    from orders',i,') t1 where ranking <=2);');
    prepare stmt from @sqlStr;
    execute stmt;
    deallocate prepare stmt;
          set i=i+1;
          end while
end
;;             
delimiter ;

调用存储过程，并查看数据结果

call insert_odata()
select * from data;

最后求所有数据每个category,sales的前两名

select category,orderid,Itemid,sales from 
(select category,orderid,Itemid,sales,
       row_number()over(partition by category,Itemid order by category,sales desc ) as ranking
from data) t1 where ranking <=2
);

一点小拓展

我在第一次写的时候，因为不知道在MySQL中使用循环需要将其放入存储过程，我的思路是将表名作为变量创建存储过程，然后再通过循环调用存储过程，导致第一个方案用了两个存储过程。

create table data (category varchar(10) not null ,orderid int(11) not null primary key ,
    Itemid varchar(30) not null ,
    sales float not null
);
#第一个存储过程
#用表作为变量
drop procedure if exists insert_odata;
delimiter ;;
create procedure insert_odata (IN temp varchar(30))
begin
    set @tempStr:=CONCAT('insert into data (select category,orderid,Itemid,sales from(
select category,orderid,Itemid,sales,
           row_number()over(partition by category order by category,sales desc ) as ranking
    from ',temp,') t1 where ranking <=2);');
    prepare stmt from @tempStr;
    execute stmt;
    deallocate prepare stmt;
end
;;
delimiter ;

#第二个 存储过程
drop procedure if exists run;
delimiter $$
create procedure run()
    begin
        DECLARE i int;
        DECLARE Tname varchar(25);
        set i=1;
        while i<=5 do
            set Tname =concat('orders',i);
            call insert_odata(Tname);
            set i=i+1;
            end while;
    end
    $$

delimiter ;
call run();
select * from data;