技術標籤：leftjoin多個on條件select 加條件sql join on 多表連線sql where between 和 andsql語句怎麼連線兩個表提交資料裡面有and就報錯

create table testA(       Id number(10) primary key,       Name varchar(10))insert into testA values(1,'小黃');insert into testA values(2,'小綠');insert into testA values(3,'小白');insert into testA values(4,'小黑');insert into testA values(5,'小花');commitcreate table testB(       Id number(10) primary key,       age number(10))insert into testB values(1,10);insert into testB values(2,11);insert into testB values(3,12);insert into testB values(4,13);commit
 

on後面加and

select * from testA a left join testB b  on a.id = b.id and b.age=10

on後面加where

select * from testA a left join testB b  on a.id = b.id where b.age=10

on 是用於消除笛卡兒積的，表連線時不加on會報錯，left join語句會從左表那裡返回所有的行，即使在右表中沒有匹配的行，on後面接and也會兼顧左連線，不管and 後面接什麼內容，左表資料都會全部展示下圖語句由於a.name =10在testA沒有匹配資料，所以與其關聯的testB也匹配不到資料。

select * from testA a left join testB b   on a.id = b.id and a.name='10'

使用where就是對連線後的結果集進行條件篩選

select*fromtestAaleftjointestBbona.id=b.idwherea.name='10'