mysql select avoid duplicate rows code example

Example 1: t-sql get duplicate rows

SELECT [CaseNumber], COUNT(*) AS Occurrences
FROM [CaseCountry]
GROUP BY [CaseNumber]
HAVING (COUNT(*) > 1)

Example 2: 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 3: update all rows mysql

UPDATE tableName SET columnName = yourValue;
#to update multiple columns:
UPDATE tableName SET column1 = value1, column2 = value2; #and so on

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 delete duplicate rows except one

DELETE FROM NAMES
 WHERE id NOT IN (SELECT * 
                    FROM (SELECT MIN(n.id)
                            FROM NAMES n
                        GROUP BY n.name) x)