Deleting Duplicate Records in SQL Server Without CTE or ROW_NUMBER

Data and Databases
1

Query to remove duplicate records by ActID without CTE/ROW_NUMBER. Retain rows with aVal=4.

DELETE FROM T WHERE ID NOT IN(SELECT MAX(ID) FROM T GROUP BY actID) AND aVal<>4;
2

hey, im not 100% sure but u might see issues with nulls in not in clause, might be better using join on the filtered duplicates, so you keep all aVal=4 rows safe. test on a sample db first.

3

hey, been tinkering with this cdeleting method. maybe a left join might catch those nulls better? also, how are u handling unexpected cases when aVal=4 isnt unique? would love to hear more ideas or edge cases u folks have noticed.

4

In my experience, it is crucial to test and validate any deletion query on a backup or a test environment before device execution in production. While using a subquery with a join helped address the potential pitfalls when handling nulls, I found that an explicit safeguard for records with aVal=4 is indispensable. By ensuring these critical records are retained, you minimize risks of data loss. This cautious approach has served me well in multiple scenarios where data integrity was paramount.

5

hey, i tried a join method instead and noticed it can be smoother for handling nulls. def test on a small backup first to catch any weird dup cases with aVal=4. using smaller batches can help if things go wrong