delete duplicate rows and need to keep one from al

问题:

This question already has answers here:

Remove duplicate rows in MySQL (25 answers)

Closed 7 years ago.

I want to delete duplicate rows based on two columns but need to keep 1 row all of them.

Duplicate rows can be more than two rows like,

ID  NAME PHONE
--  ---- ----
1   NIL  1234 
2   NIL  1234 
3   NIL  1234 
4   MES  5989

I want to delete any of 2 rows from above 3 and keep 1 row.

回答1:

DELETE  a
FROM    tableA a
        LEFT JOIN
        (
            SELECT MIN(ID) ID, Name, Phone
            FROM    TableA
            GROUP   BY Name, Phone
        ) b ON  a.ID = b.ID AND
                a.NAme = b.Name AND
                a.Phone = b.Phone
WHERE   b.ID IS NULL

• SQLFiddle Demo

After you have executed the delete statement, enforce a unique constraint on the column so you cannot insert duplicate records again,

ALTER TABLE TableA ADD CONSTRAINT tb_uq UNIQUE (Name, Phone)

回答2:

DELETE
FROM Table
WHERE Table.id NOT IN  (  
    SELECT MIN(idTable) idtable
    FROM idTable
    GROUP BY name, phone)