Question

I have the following problem:

I have table:

TEST_TABLE
x_Id|y_Id
---------
   2|   7
   2|   8
   3|   7
   4|   7
   5|   8

I want remove record if x_Id has y_Id(7) and y_Id(8). And update y_Id to 7 if y_Id = 8 and y_Id(7) is not exist in the unique x_Id.

x_Id and y_Id is composite key.

Example of result:

TEST_TABLE
x_Id|y_Id
---------
   2|   7
   3|   7
   4|   7
   5|   7

Answer 1

These queries do not use corelated subqueries (ones where they must be executed for every row of the outer query), so they should be quite efficient.

delete from test_table
where y_id = 8
and x_id in (select x_id from test_table where y_Id = 7);

update test_table set y_id = 7
where x_id in (select x_id from test_table where y_id = 8)
and x_id not in (select x_id from test_table where y_id = 7);