Question

I’m trying to update one column in a subset of a table but I can’t figure out how to do it in a clean and efficient manner.

Consider the following:

// MyTable
id    name  flag
0     Steve 0
1     Bob   0
...
10500 Rick  0

I want to change flag to 1 but only for some of the cases. I tried to use

UPDATE MyTable
SET flag = 1
WHERE id <= 500

But obviously that does not work because the subquery returns more than one value. Technically, I could do it like this:

UPDATE MyTable SET flag = 1 WHERE id = 0
UPDATE MyTable SET flag = 1 WHERE id = 1
...
UPDATE MyTable SET flag = 1 WHERE id = 500

But who wants to do it like that? 🙂 Is there a better way for me to format this query and only update those which match an inequality?

EDIT

To clarify exactly what’s going on: when I say ‘some of these cases’ I only mean those which match the inequality, in this case id <= 500

When I run UPDATE MyTable SET flag = 1 WHERE id <= 500 I get the following error:

Subquery returned more than 1 value. 
This is not permitted when the subquery follows =, !=, <, <= , >, >=
    or when the subquery is used as an expression.

Answer 1

SInce your query does not have a subquery, I would suspect that you have a poorly wrtten trigger on the table that expects only one record at a time to be updated. This needs to be fixed as no trigger should ever be written on this assumption. Triggers in SQL Server need to perform only set-based operations as they work against the whole set not one row at a time.