remove duplicates mysql code example

Example 1: query postgres delete duplicates

DELETE FROM dups a USING (
      SELECT MIN(ctid) as ctid, key
        FROM dups 
        GROUP BY key HAVING COUNT(*) > 1
      ) b
      WHERE a.key = b.key 
      AND a.ctid <> b.ctid

Example 2: mysql remove duplicates

DELETE FROM table_name WHERE id 
       NOT IN ( SELECT id FROM table_name 
                   GROUP BY field_1, field_2)

Example 3: mysql delete duplicate rows but keep one

DELETE c1 FROM contacts c1
INNER JOIN contacts c2 
WHERE
    c1.id > c2.id AND 
    c1.email = c2.email;

Example 4: how to delete all duplicate items in mysql

DELETE FROM FriendsData WHERE fID 
       NOT IN ( SELECT fID FROM FriendsData 
                   GROUP BY UserID, FriendsUserID, IsSpecial, CreatedBy)

Example 5: mysql delete duplicate rows

DELETE FROM table_name 
WHERE 
	id IN (
	SELECT 
		id 
	FROM (
		SELECT 
			id,
			ROW_NUMBER() OVER (
				PARTITION BY field_1
				ORDER BY field_1) AS row_num
		FROM 
			table_name
		
	) t
    WHERE row_num > 1
);

Example 6: mysql remove duplicates

DELETE t1 FROM contacts t1
INNER JOIN contacts t2 
WHERE 
    t1.id < t2.id AND 
    t1.email = t2.email;Code language: SQL (Structured Query Language) (sql)