SQL Server. Delete from Select - sql

Question

I am using SQL Server 2012, and have the following query. Let's call this query A.
SELECT a.col, a.fk
FROM Table1 a
INNER JOIN (
select b.col
from Table1 b
group by b.col
having count(*) > 1)
b on b.col = a.col
I want to delete only the rows returned from query A, specifically rows that match the returned col AND fk
I am thinking of doing the following, but it will only delete rows that match on the col.
delete from Table1
where col in (
SELECT a.col
FROM Table1 a
INNER JOIN (
select b.col
from Table1 b
group by b.col
having count(*) > 1)
b on b.col = a.col)
)

Answer 1

Use delete from Join syntax
delete t1
from table1 t1
INNER JOIN (SELECT a.col, a.fk
FROM Table1 a
INNER JOIN (
select b.col
from Table1 b
group by b.col
having count(*) > 1)
b on b.col = a.col) t2
ON t1.col1=t2.col1 and t1.fk=t2.fk

Answer 2

you can combine col and fk fields to be another unique filed to retrieve wanted rows
delete from Table1
where cast(col as varchar(50))+'//'+cast(fk as varchar(50)) in (
SELECT cast(a.col as varchar(50))+'//'+cast(a.fk as varchar(50))
FROM Table1 a
INNER JOIN (
select b.col
from Table1 b
group by b.col
having count(*) > 1)
b on b.col = a.col)
)

Answer 3

You can express Query A like this:
SELECT col, fk
FROM (
SELECT a.col, a.fk, COUNT(*) OVER (PARTITION BY a.col) AS [count]
FROM Table1 a
) counted
WHERE [count] > 1
Which leads to a nice way to do the DELETE using a CTE:
;WITH ToDelete AS (
SELECT a.col, a.fk, COUNT(*) OVER (PARTITION BY a.col) AS [count]
FROM Table1 a
)
DELETE FROM ToDelete
WHERE [count] > 1
This does give the same result as the DELETE statement in your question though.
If you want to delete all but one row with the duplicate col value you can use something like this:
;WITH ToDelete AS (
SELECT a.col, a.fk
, ROW_NUMBER() OVER (PARTITION BY a.col ORDER BY a.fk) AS [occurance]
FROM Table1 a
)
DELETE FROM ToDelete
WHERE [occurance] > 1
The ORDER BY clause will determine which row is kept.