How to write such a SQL statement

Question

There is a table called user which structure is like so:

id | ... | qq_unionid | wx_unionid

1  | ... | nfdufdflfl | fdfgnugdgdll

2  | ... | NULL       | dfdfjjdfjd

3  | ... | fdfnfdfull | NULL 

4  | ... | NULL       | NULL 

Now, what i want to do is move the two fields qq_unionid and wx_unionid into another table thirdpartyinfo whick looks like so:

id | user_id | qq_nickname | wx_nickname

1  | 1       | Petter      | Petter

2  | 2       | null        | Gorgine

3  | 3       | Julia       | NULL

and what i expected is like below:

id | user_id | qq_unionid | wx_unionid | qq_nickname | wx_nickname

1  | 1       | dfdfdj     |  fdjfkjdd  | Petter      | Petter

2  | 2       | NULL       |  fdjkfjd   | NULL        | Gorgine

3  | 3       | dfdfdfdff  |  NULL      | Julia       | NULL

I do not know how to write SQL statement to move the two fields into new table. Please give me a hand. Thanks so much.

Answer 1

You can SELECT the information without moving the columns to the other table. You can also use this query to create a view .

SELECT t.id, t.user_id, u.qq_unionid, u.wx_unionid, t.qq_nickname, t.wx_nickname
FROM thirdpartyinfo t INNER JOIN `user` u ON t.user_id = u.id

In case you want to create new columns on table thirdpartyinfo and set the values from user into the new columns you can do the following:

ALTER TABLE thirdpartyinfo ADD COLUMN qq_unionid VARCHAR(255) NULL,
  ADD COLUMN wx_unionid VARCHAR(255) NULL

The two columns are available now in the thirdpartyinfo table. Make sure you are using the correct / needed column definition. After that you can set the values from user table to the new columns, using UPDATE :

UPDATE thirdpartyinfo INNER JOIN `user` ON thirdpartyinfo.user_id = `user`.id 
  SET thirdpartyinfo.qq_unionid = `user`.qq_unionid,
      thirdpartyinfo.wx_unionid = `user`.wx_unionid 

Answer 2

If I understand correctly, what you want is to make thirdpartyinfo table having 2 new fields (ie qq_unionid, wx_unionid) and fill these 2 fields with data from user table.

First of all, you need to create those 2 new columns in the thirdpartyinfo table:

ALTER TABLE thirdpartyinfo ADD qq_unionid varchar(40) NULL, ADD wx_unionid varchar(40) NULL

Next you can use MERGE to fill in the data from user table:

MERGE INTO thirdpartyinfo target 
USING (SELECT u.id, u.qq_unionid, u.wx_unionid FROM user u) source
ON (target.id=source.id) 
WHEN MATCHED THEN 
    UPDATE 
    SET target.qq_unionid = source.qq_unionid, 
        target.wx_unionid = source.wx_unionid;