How to return NULL when result is empty?

select
  (Your entire current Select statement goes here) as Alias
from 
  dual

dual is a built in table with a single row that can be used for purposes like this. In Oracle this is mandatory. MySQL supports it, but you can also just select a single value without specifying a table, like so:

select
  (Your entire current Select statement goes here) as Alias

In either case you're selecting a single value. This means that:

  • If your select returns one value, that value is returned.
  • If your select statement returns one column, but no rows, NULL will be returned.
  • If your select statement returns multiple columns and/or multiple rows, this won't work and the query fails.

Late reply but I think this is the easiest method:

SELECT
   IFNULL((SELECT your query), NULL)

An easy way to do this is with aggregation:

select max(col)
from t
where <your condition here>

This always returns one row. If there is no match, it returns NULL.

Tags:

Mysql

Sql

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