Two-table join query. When a data cannot match each other, use the default value instead.

For example, a class renewal table

Create course Table

Sid sname
1 Language
2. Mathematics
3 English
.......

 

Table B

Id Sid Fen name
1 1 100 Zhang San
2 1 89 Li Si
3 1 95 Wang Wu
4 2 89 Zhang San
5 3 78 Wang Wu
6 2 99 Wang Wu
234 hackers

 

 

Select tableb. ID, tableb. Sid, tableb. Fen, isnull (tablea. sname, 'Why didn't this subject '), tableb. Name
As subject
From tableb left Outer Join
Tablea on tableb. Sid = tablea. Sid