Re: using alias in where clause
Larry Martell <[email protected]>
| Newsgroups | gmane.comp.db.mysql.general |
|---|---|
| Message-ID | <CACwCsY4qn6hXmE+GJfLx+3i1LTdH9gzJDaH=cRxQ4Ot+x=B=LA@mail.gmail.com> |
On Mon, Jan 25, 2016 at 8:01 PM, Rebecca Love <[email protected]> wrote: > Have you tried using a select case statement for ftag? How would that help? Unless I'm missing something, I'd still have to have a reference to the column alias in the where clause. >> On Jan 25, 2016, at 6:39 PM, Larry Martell <[email protected]> wrote: >> >> On Mon, Jan 25, 2016 at 7:27 PM, Reindl Harald <[email protected]> wrote: >>> >>> >>> Am 26.01.2016 um 01:16 schrieb Larry Martell: >>>> >>>> I know I cannot use an alias in a where clause, but I am trying to >>>> figure out how to achieve what I need. >>>> >>>> If I could have an alias in a where clause my sql would look like this: >>>> >>>> SELECT IFNULL(f_tag_bottom, >>>> IFNULL(f_tag_bottom_major_axis, >>>> IFNULL(f_tag_bottom_minor_axis, >>>> IFNULL(f_tag_ch_x_bottom, >>>> IFNULL(f_tag_ch_y_bottom, NULL))))) as ftag, >>>> STDDEV(ch_x_top) >>>> FROM data_cst >>>> WHERE ftag = 'E-CD7' >>>> GROUP BY wafer_id, lot_id >>>> >>>> But I can't use ftag in the where clause. I can't put it in a having >>>> clause, as that would exclude the already aggregated rows and I want >>>> to filter then before the aggregation. Anyone have any idea how I can >>>> do this? >>> >>> >>> why would you want to do that? >>> it would make the where clause not be able to use proper indexes >> >> I do not know which of the 5 f_tag_* columns will be populated and I >> need to filter on the one that is populated. >> >> -- >> MySQL General Mailing List >> For list archives: http://lists.mysql.com/mysql >> To unsubscribe: http://lists.mysql.com/mysql >> > -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql