Searches for records that exist in one table and do not exist in the other table.

For example, two tables: T1 and T2. query records that exist in Table T1 but do not exist in Table T2.

Assume that the ID field is used as the associated field.

Method 1: the fields of the two tables must be completely consistent.

Select *
From T1
Minus
Selecct * From T2

 

Method 2:

Select * from T1
Where not exists (select 1 from T2 where t1.id = t2.id)

 

Method 3:

Select * from T1
Where id not in (select ID from T2)

 

Method 4: t2.id cannot be blank

Select T1 .*
From T1
Left join T2 on t1.id = t2.id
Where t2.id is null