How can i remove rows from several tables with SQL? - sql

Question

I have a 3 tables:
mainTable:
id | uniqField
--------------
1 | 1111
2 | 1111
3 | 2222
4 | 2222
5 | 3333
6 | 4444
table1:
id|name|deleted
----------
1|Mike|0
2|Mike|0
5|John|0
table2:
id|name|deleted
----------
3|Peke|0
4|Peke|0
6|Vels|0
That tables bind by id field.
Now i want to remove duplicates from this tables. For mainTable i can use:
DELETE mainTable
FROM mainTable
LEFT OUTER JOIN (
SELECT MIN(id) as RowId, uniqField
FROM mainTable
GROUP BY uniqField
) as KeepRows ON
mainTable.id= KeepRows.RowId
WHERE
KeepRows.RowId IS NULL
But in tables1 and table2 i want to set deleted field to 0->1 to duplicates I mean:
1 | 1111
2 | 1111 -> duplicate->remove
1|Mike|0
2|Mike|0->duplicate-> 0->1

Answer 1

Try this one -
SET NOCOUNT ON;
DECLARE #mainTable TABLE
(
id INT,
uniqField INT
)
INSERT INTO #mainTable (id, uniqField)
VALUES (1, 1111), (2, 1111), (3, 2222), (4, 2222), (5, 3333), (6, 4444)
DECLARE #deleted TABLE (id INT)
;WITH cte AS
(
SELECT *, RowNum = ROW_NUMBER() OVER (PARTITION BY uniqField ORDER BY 1/0)
FROM #mainTable
)
DELETE FROM cte
OUTPUT DELETED.id INTO #deleted
WHERE RowNum > 1
DECLARE #table1 TABLE
(
id INT,
uniqField VARCHAR(10),
deleted BIT
)
DECLARE #table2 TABLE
(
id INT,
uniqField VARCHAR(10),
deleted BIT
)
INSERT INTO #table1 (id, uniqField, deleted)
VALUES (1, 'Mike', 0), (2, 'Mike', 0), (5, 'John', 0)
INSERT INTO #table2 (id, uniqField, deleted)
VALUES (3, 'Peke', 0), (4, 'Peke', 0), (6, 'Vels', 0)
UPDATE #table1
SET deleted = 1
FROM #deleted
WHERE [#deleted].id = [#table1].id
UPDATE #table2
SET deleted = 1
FROM #deleted
WHERE [#deleted].id = [#table2].id
SELECT * FROM #table1
SELECT * FROM #table2
Output -
id uniqField deleted
----------- ---------- -------
1 Mike 0
2 Mike 1
5 John 0
id uniqField deleted
----------- ---------- -------
3 Peke 0
4 Peke 1
6 Vels 0