Let's say we have a SQL request, such as select * from employees. If I want to know only the number of rows, then this can be done by select count(*) from employees.
The problem is that this require modifying the SQL request which may require some parsing. If the request is a string SQL_request, I would like to write something generic, simple and robust like: select count(*) from (SQL_request), but the resulting request (that is select count(*) from (select * from employees)) is not a correct one.
It should be noted that in some cases we can do such construction. E.g. if one want the top 1000 rows of a request, then one can do (SQL_request) limit 1000.
Could there be a way to encapsulate a generic SQL table request so that one could get the number of rows?
...but the resulting request that is
select count(*) from (select * from employees))is not a correct one...
You are using your query as a "table expression" but you forgot to assign an alias to it. Try:
select count(*) from (select * from employees)) x
See the x at the end?