87.多表联结导致记录重复的案例

--测试数据
CREATE TABLE ta(id int)
INSERT ta SELECT 1

CREATE TABLE tb(id int)
INSERT tb SELECT 1
UNION ALL SELECT 1

CREATE TABLE tc(id int)
INSERT tc SELECT 1
UNION ALL SELECT 1

--查询
SELECT * 
FROM ta a 
	JOIN tb b ON a.id=b.id
	JOIN tc c ON a.id=c.id

/*--结果
id          id          id          
----------- ----------- ----------- 
1           1           1
1           1           1
1           1           1
1           1           1
--*/