Re: Counting unique rows as an aggregate.

Richard Broersma wrote:
> On Mon, Sep 29, 2008 at 4:36 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> > SELECT count(distinct make), count(distinct color) from table WHERE >criteria<;
>
> Is this in the SQL spec? I didn't know Agg functions could do this?
>

Yes. SQL92 6.5

<set function specification> ::=
COUNT <left paren> <asterisk> <right paren>
| <general set function>

<general set function> ::=
<set function type>
<left paren> [ <set quantifier> ] <value expression> <right paren>

<set function type> ::=
AVG | MAX | MIN | SUM | COUNT

<set quantifier> ::= DISTINCT | ALL

I never realised that you could use it for more than count though. In
8.3.3, it worked for sum/avg/stddev/variance.

klint.

--
Klint Gore
Database Manager
Sheep CRC
A.G.B.U.
University of New England
Armidale NSW 2350

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