When two sets are given
s1 ={ a,b,c,d} s2={b,c,d,a}
(i.e)
TableA
Item
a
b
c
d
TableB
Item
b
c
d
a
How to write Sql query to display "Elements in tableA and tableB are equal". [Without using SP or UDF]
Output
Elements in TableA and TableB contains identical sets
Use the EXCEPT operation to subtract the set returned by the first query from the set returned by the second query. If the result is an empty set then they are equivalent.
By using UNION, UNION ALL, EXCEPT, and INTERSECT, we can compare two queries and get the necessary output as per our requirement. Given examples are simple to follow, we can have complex queries and can apply the mentioned constructs in them and can compare.
Comparing the Results of the Two Queries The solution to this is very simple. Run both queries using a UNION to combine the results! The UNION operator returns unique records. If the two results sets are identical the row count will remain the same as the original query.
Use:
SELECT CASE
WHEN COUNT(*) = (SELECT COUNT(*) FROM a)
AND COUNT(*) = (SELECT COUNT(*) FROM b) THEN 'Elements in TableA and TableB contains identical sets'
ELSE 'TableA and TableB do NOT contain identical sets'
END
FROM (SELECT a.col
FROM a
INTERSECT
SELECT b.col
FROM b) x
Test with:
WITH a AS (
SELECT 'a' AS col
UNION ALL
SELECT 'b'
UNION ALL
SELECT 'c'
UNION ALL
SELECT 'd'),
b AS (
SELECT 'b' AS col
UNION ALL
SELECT 'c'
UNION ALL
SELECT 'd'
UNION ALL
SELECT 'a')
SELECT CASE
WHEN COUNT(*) = (SELECT COUNT(*) FROM a)
AND COUNT(*) = (SELECT COUNT(*) FROM b) THEN 'yes'
ELSE 'no'
END
FROM (SELECT a.col
FROM a
INTERSECT
SELECT b.col
FROM b) x
Something like this, using FULL JOIN
:
SELECT
CASE
WHEN EXISTS (
SELECT * FROM s1 FULL JOIN s2 ON s1.Item = s2.Item
WHERE s1.Item IS NULL OR s2.Item IS NULL
)
THEN 'Elements in tableA and tableB are not equal'
ELSE 'Elements in tableA and tableB are equal'
END
This has the virtue of short-circuiting on the first non-match, unlike other solutions that require 2 full scans of each table (once for the COUNT(*), once for the JOIN/INTERSECT).
Estimated cost is significantly less than other solutions.
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With