Re: using alias in where clause
- Date: Mon, 25 Jan 2016 19:39:29 -0500
- From: Larry Martell <larry.martell@xxxxxxxxx>
- Subject: Re: using alias in where clause
On Mon, Jan 25, 2016 at 7:27 PM, Reindl Harald <h.reindl@xxxxxxxxxxxxx> 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_ch_y_bottom, NULL))))) as ftag,
>> 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