Mysql Left Join Where On

Select t1.id, t2.id
From T1
Left join T2 on t1.id = t2.id and t1.id> 1 and t2.id <> 3

In left join of MySQL, the conditions placed after on are different from those after where;

1. On is followed by T2. therefore, the above t1.id> 1 does not work. Remember, remember;

2. The WHERE clause will affect the final result. Therefore, if t2.id <> 3 is placed after the on clause and where clause, different results will be returned;

For example, the following script returns some data later than script 2.

Select * From Test2
Left join test1 on test2.id = test1.id and test1.id <> 3
Where test2.id <> 6;
Select * From Test2
Left join test1 on test2.id = test1.id
Where test2.id <> 6 and test1.id <> 3;