What does it mean by select 1 from table?

mysql sql plsql
Microsoft Developer picture Microsoft Developer · Aug 24, 2011 · Viewed 261.4k times · Source

I have seen many queries with something as follows.

Select 1  
From table

What does this 1 mean, how will it be executed and, what will it return?

Also, in what type of scenarios, can this be used?

Answer

Sahil Muthoo picture Sahil Muthoo · Aug 24, 2011

select 1 from table will return the constant 1 for every row of the table. It's useful when you want to cheaply determine if record matches your where clause and/or join.

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