delete duplicate rows matching with other table - postgresql

Question

I have two tables
Table A Table B
-------- ---------
a b c a b c
a b c a b c
a b c a b c
e f g a b c
h i j e f g
k l m k l m
k l m
x y z
s t u
a b c
a b c
Now i want to remove rows in Table B matching on column 1, 2 and 3 with table A where the count of each duplicate row in Table B should be less than or equal to table A.
So the output should be
Table A Table B
-------- ---------
a b c a b c
a b c a b c
a b c a b c
e f g e f g
h i j k l m
k l m x y z
s t u
I have tried using inner join and intersect but failed to get the desired result.

Answer 1

Try:
DELETE FROM tableB
WHERE ctid IN (
SELECT BB.ctid
FROM (
SELECT a, b, c, count(*) cnt
FROM tablea
GROUP BY a, b, c
) AA
JOIN (
SELECT ctid,
a, b, c,
row_number() over (partition by a,b,c) cnt
FROM tableb
) BB
ON AA.a = BB.a
AND AA.b = BB.b
AND AA.c = BB.c
AND AA.cnt < BB.cnt
)
demo: http://sqlfiddle.com/#!12/73e99/1

Answer 2

I think if table isn't big the simply way is to delete all rows from TableB which exist in TableA and then insert TableA into TableB. Another ways IMHO are required at least a primary key in TableB.
DELETE FROM TableB
WHERE EXISTS(SELECT * FROM TableA
WHERE C1=TableA.C1
AND C2=TableA.C2
AND C3=TableA.C3) ;
INSERT INTO TableB SELECT * FROM TableA;