why would you use WHERE 1=0 statement in SQL?

Question

I saw a query run in a log file on an application. and it contained a query like:

SELECT ID FROM CUST_ATTR49 WHERE 1=0

what is the use of s

Answer 1

quoted from Greg

If the list of conditions is not known at compile time and is instead built at run time, you don't have to worry about whether you have one or more than one condition. You can generate them all like:

and

and concatenate them all together. With the 1=1 at the start, the initial and has something to associate with.

I've never seen this used for any kind of injection protection, as you say it doesn't seem like it would help much. I have seen it used as an implementation convenience. The SQL query engine will end up ignoring the 1=1 so it should have no performance impact.

Why would someone use WHERE 1=1 AND in a SQL clause?