On Mon, Jan 25, 2016 at 7:27 PM, Reindl Harald <h.rei...@thelounge.net> 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
