database - 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 such a query that is bound to return nothing?

Answer 1

A query like this can be used to ping the database. The clause:

WHERE 1=0

Ensures that non data is sent back, so no CPU charge, no Network traffic or other resource consumption.

A query like that can test for:

• server availability
• CUST_ATTR49 table existence
• ID column existence
• Keeping a connection alive
• Cause a trigger to fire without changing any rows (with the where clause, but not in a select query)
• manage many OR conditions in dynamic queries (e.g WHERE 1=0 OR <condition>)