MySQL实现全关联 full outer join

SQL LEFT JOIN 关键字

LEFT JOIN 关键字会从左表 (table_name1) 那里返回所有的行,即使在右表 (table_name2) 中没有匹配的行。

LEFT JOIN 关键字语法

SELECT column_name(s)
FROM table_name1
LEFT JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

注释:在某些数据库中, LEFT JOIN 称为 LEFT OUTER JOIN。

SQL RIGHT JOIN 关键字

RIGHT JOIN 关键字会右表 (table_name2) 那里返回所有的行,即使在左表 (table_name1) 中没有匹配的行。

RIGHT JOIN 关键字语法

SELECT column_name(s)
FROM table_name1
RIGHT JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

注释:在某些数据库中, RIGHT JOIN 称为 RIGHT OUTER JOIN。

SQL FULL JOIN 关键字

只要其中某个表存在匹配,FULL JOIN 关键字就会返回行。

FULL JOIN 关键字语法

SELECT column_name(s)
FROM table_name1
FULL JOIN table_name2 
ON table_name1.column_name=table_name2.column_name

注释:在某些数据库中, FULL JOIN 称为 FULL OUTER JOIN。

 

很苦恼 MySQL不支持全关联,只能实现左右关联,通过观察左右关联的结果数据发现,我们可以根据左右关联的结果实现 全关联:

思路很简单:
左关联结果表:
tempa
右关联结果表:
tempb
全关联结果表:
select * from (
select * from tempa 
union 
select * from tempb) c;

 用例验证:

  1.建表语句(基础表)

drop table if exists data_stock1;
create table data_stock (account varchar(10),amount1 int,init_date varchar(20));
INSERT INTO `data_stock1` VALUES ('2002', 210, '20170101');
INSERT INTO `data_stock1` VALUES ('2001', 70, '20170101');
INSERT INTO `data_stock1` VALUES ('2001', 200, '20170102');
INSERT INTO `data_stock1` VALUES ('2001', 30, '20170103');
INSERT INTO `data_stock1` VALUES ('2002', 10, '20170102');

drop table if exists data_stock1;
create table data_stock (account varchar(10),amount2 int,init_date varchar(20));
INSERT INTO `data_stock2` VALUES ('2003', 70, '20170102');
INSERT INTO `data_stock2` VALUES ('2001', 200, '20170101');
INSERT INTO `data_stock2` VALUES ('2001', 30, '20170102');
INSERT INTO `data_stock2` VALUES ('2002', 10, '20170102');
INSERT INTO `data_stock2` VALUES ('2003', 30, '20170101');

  2.全联接生成实验

SELECT * from data_stock1 ORDER BY init_date;
SELECT * from data_stock2 ORDER BY init_date;
-- 左联 left JOIN 结果存到临时表
Drop table  if EXISTS tempA;
create TABLE tempA(account VARCHAR(10),amount1 int,init_date VARCHAR(20),account1 VARCHAR(10),amount2 int,init_date1 VARCHAR(10)) AS

-- 插入的数据
select a.*,b.account as account1,amount2,b.init_date as init_date1 from data_stock1 a LEFT JOIN data_stock2 b
 on a.account= b.account and a.init_date=b.init_date;

-- 右联 right JOIN  存到临时表
Drop table  if EXISTS tempB;
create TABLE tempB(account VARCHAR(10),amount1 int,init_date VARCHAR(20),account1 VARCHAR(10),amount2 int,init_date1 VARCHAR(10)) AS
-- 插入的数据
select a.*,b.account as account1,amount2,b.init_date as init_date1 from data_stock1 a RIGHT JOIN data_stock2 b
 on a.account= b.account and a.init_date=b.init_date;

-- 全联 full outer JOIN
Drop table if EXISTS tempc;
create table tempc(account VARCHAR(10),amount1 int,init_date VARCHAR(20),account1 VARCHAR(10),amount2 int,init_date1 VARCHAR(10)) AS
-- 插入的数据

SELECT * from (
select * from tempa
union 
SELECT * from tempb) b;

     

  3.后续操作,计算amount1 + amount2

SELECT IFNULL(account,account1),IFNULL(init_date,init_date1), IFNULL(amount1,0)+IFNULL(amount1,0) AS
total from tempc where (account=account1) and (init_date=init_date1) ;

 

 

posted @ 2018-04-17 11:48  QualityAssurance21  阅读(31076)  评论(0编辑  收藏  举报