[SOLVED] Why would someone use WHERE 1=1 AND <conditions> in a SQL clause?

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

Why would someone use WHERE 1=1 AND <conditions> in a SQL clause (Either SQL obtained through concatenated strings, either view definition)

I've seen somewhere that this would be used to protect against SQL Injection, but it seems very weird.

If there is injection WHERE 1 = 1 AND injected OR 1=1 would have the same result as injected OR 1=1.

What about the usage in a view definition?

Solution

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 <condition>

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.