Question

DELETE abc 
FROM abc INNER JOIN xyz ON 
abc.RECORD_TYPE = xyz.RECORD_TYPE AND 
abc.IN = xyz.IN 
OPTION (MERGE JOIN, LOOP JOIN)

can anyone tell me what exactly the query doing ?

Answer 1

This DELETE all the records from the table abc with JOIN to another table. It deletes all the records in the table abc that has a RECORD_TYPE value equal to the RECORD_TYPE in the other table AND in the same time the value IN are equals in the two table.

It is a normal DELETE clause, Where the FROM can contain extra joined table as specified by the documentation:

FROM clause:

This extension, specifying a join, can be used instead of a subquery
in the WHERE clause to identify rows to be removed.