I have a query like this:

```
select author1 
from books_group 
where category='cse' 
union 
select author2 
from books_group 
where category='cse' 
union 
select author3 
from books_group 
where category='cse'

```

the above query union the all the records that are comes from three select commands..

my task is to count the number of records we have after the execution of above sql command...

and i trying the below query but it gives an error..

" select count(\*) from (select author1 from books\_group where category='cse' union select author2 from books\_group where category='cse' union select author3 from books\_group where category='cse') "

then, how to get the number of recors after the union operation..???