Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
453 views
in Technique[技术] by (71.8m points)

mysql - How to find non-existing data from another Table by JOIN?

I have two tables TABLE1 which looks like:

id      name     address
1       mm     123
2       nn     143

and TABLE2 w/c looks like:

name     age
mm      6
oo      9

I want to get the non existing names by comparing the TABLE1 with the TABLE2.

So basically, I have to get the 2nd row, w/c has a NN name that doesn't exist in the TABLE2, the output should look like this:

id      name     address
2      nn      143

I've tried this but it doesn't work:

SELECt  w.* FROM TABLE1 W INNER JOIN TABLE2 V
  ON W.NAME <> V.NAME

and it's still getting the existing records.

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

An INNER JOIN doesn't help here.

One way to solve this is by using a LEFT JOIN:

SELECT w.* 
FROM TABLE1 W 
LEFT JOIN TABLE2 V ON W.name = V.name
WHERE ISNULL(V.name);

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...