does the select operation eliminate duplicates IN SQL code example
Example 1: sql delete duplicate
-- Oracle
DELETE films
WHERE rowid NOT IN (
SELECT min(rowid)
FROM films
GROUP BY title, uk_release_date
);
Example 2: 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;