There are two tables A and B. You are retreiving data from both tables where all rows from B table and only matching rows from A table should be displayed. Which of the following types of joins will you apply between A and B tables?
- Inner join
- Left outer join
- Right outer join
- Self join
Use left outer hoin or right outer join.
For example, the following satisfy your requirement.
select * from tableB
Left outer join tableA
on tableB.ID= tableA.ID
Or
select * from tableA
Right outer join tableB
on tableA.ID= tableB.ID
Better way to understand:
Easy, I would go with (B).
SELECT * FROM B x
LEFT JOIN A y
on x.someColName = y.someColname
EDIT: can also use Right join
SELECT * FROM A x
RIGHT OUTER JOIN B y
on x.someColName = y.someColname
这看起来像是家庭作业,但它已经足够简单了,我只会说你要求B LEFT JOIN A
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.