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From John English <john.fore...@gmail.com>
Subject Re: retrieving records based on a single column contents
Date Sat, 02 May 2015 13:11:58 GMT
On 01/05/2015 19:54, Bob M wrote:
> Thanks John
>
> I wasn't sure how to enter NULL into an integer field and so col3 has many
> zeroes as well as 1, 2, 3, 4, etc.
>
> and so
>
> (a) do your suggestions change at all ?

Replace "IS NOT NULL" with "<> 0" if you're using 0 instead of NULL. The second 
suggestion I gave should still work if col3 is never negative.

> (b) how do you enter NULL into an integer field ?

Just use NULL as the value... will work as long as the column is not defined 
with a NOT NULL constraint. e.g. "UPDATE mytable SET col3=NULL WHERE col3=0" 
will replace all zeroes with NULLs in col3.

> (c) how do you set up col3 to be indexed ?

CREATE INDEX foo ON mytable(col3 DESC)
     -- (since you'll presumably want descending order of values)

-- 
John English

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