SQL

Query to remove duplicate rows from a table

DELETE FROM Customers WHERE ROWID(SELECT MAX (rowid) FROM Customers C WHERE CustomerNumber = C.CustomerNumber);

sql delete duplicate rows

WITH cte AS (
    SELECT 
        contact_id, 
        first_name, 
        last_name, 
        email, 
        ROW_NUMBER() OVER (
            PARTITION BY 
                first_name, 
                last_name, 
                email
            ORDER BY 
                first_name, 
                last_name, 
                email
        ) row_num
     FROM 
        sales.contacts
)
DELETE FROM cte
WHERE row_num > 1;

sql delete duplicate rows but keep one

# Step 1: Copy distinct values to temporary table
CREATE TEMPORARY TABLE tmp_user (
    SELECT id, name 
    FROM user
    GROUP BY name
);

# Step 2: Remove all rows from original table
DELETE FROM user;

# Step 3: Remove all rows from original table
INSERT INTO user (SELECT * FROM tmp_user);

# Step 4: Remove temporary table
DROP TABLE tmp_user;

sql query to delete duplicate records

--ID should be primary key

--get duplicate records using RANK
SELECT E.ID, 
    E.firstname, 
    E.lastname, 
    E.country, 
    T.rank
FROM [SampleDB].[dbo].[Employee] E
  INNER JOIN
(
 SELECT *, 
        RANK() OVER(PARTITION BY firstname, 
                                 lastname, 
                                 country
        ORDER BY id) rank
 FROM [SampleDB].[dbo].[Employee]
) T ON E.ID = t.ID;

--delete duplications
DELETE E
    FROM [SampleDB].[dbo].[Employee] E
         INNER JOIN
    (
        SELECT *, 
               RANK() OVER(PARTITION BY firstname, 
                                        lastname, 
                                        country
               ORDER BY id) rank
        FROM [SampleDB].[dbo].[Employee]
    ) T ON E.ID = t.ID
    WHERE rank > 1;

delete duplicate data from table

WITH CTE([FirstName], 
    [LastName], 
    [Country], 
    DuplicateCount)
AS (SELECT [FirstName], 
           [LastName], 
           [Country], 
           ROW_NUMBER() OVER(PARTITION BY [FirstName], 
                                          [LastName], 
                                          [Country]
           ORDER BY ID) AS DuplicateCount
    FROM [SampleDB].[dbo].[Employee])
DELETE FROM CTE
WHERE DuplicateCount > 1;
/*will delete the duplicate value*/