The problem is that these two queries are each returning more than one row:
select isbn from dbo.lending where (act between @fdate and @tdate) and (stat ='close')
select isbn from dbo.lending where lended_date between @fdate and @tdate
You have two choices, depending on your desired outcome. You can either replace the above queries with something that's guaranteed to return a single row (for example, by using SELECT TOP 1
), OR you can switch your =
to IN
and return multiple rows, like this:
select * from dbo.books where isbn IN (select isbn from dbo.lending where (act between @fdate and @tdate) and (stat ='close'))