Thread: ARRAY_AGG and COUNT

<span class="Apple-style-span" style="font-family: verdana, geneva, lucida, 'lucida grande', arial, helvetica,
sans-serif;font-size: 13px; -webkit-border-horizontal-spacing: 1px; -webkit-border-vertical-spacing: 1px; ">Hi all!<br
/><br/>I am working on a query to identify which group ids exists within a spatial cell. In this case i have the GREG
tablewhich has polygon data and the priogrid_land which have the cell polygon.<br />I want to identify which and how
manyGREG group ids exists within each of the priogrid_land cells.<br /><br />I have tried the below query, but i cannot
finda way to select only DISTINCT into the ARRAY_AGG function. I also do not want 0 to be included in the array or 0 to
becounted.<br /><br />Any suggestions on how to accomplish the above?<br /> Thanks!<br /><br /><div
style="margin-right:20px; margin-bottom: 20px; margin-left: 20px; margin-top: 5px; "><div class="smallfont"
style="font:normal normal normal 11px/normal verdana, geneva, lucida, 'lucida grande', arial, helvetica, sans-serif;
margin-bottom:2px; "> Code:</div><pre class="alt2" style="background-color: rgb(244, 244, 244); color: rgb(0, 0, 0);
font-weight:normal; font-style: normal; font-variant: normal; margin-top: 0px; margin-right: 0px; margin-bottom: 0px;
margin-left:0px; padding-top: 6px; padding-right: 6px; padding-bottom: 6px; padding-left: 6px; border-top-width: 1px;
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inset;border-bottom-style: inset; border-left-style: inset; border-color: initial; width: 640px; height: 98px;
overflow-x:auto; overflow-y: auto; "> 
<span class="highlight" style="color: rgb(255, 0, 0); font-weight: bold; ">SELECT priogrid_land.gid,
priogrid_land.cell,array_to_string(array_agg(g1id), ';') AS g1list, array_to_string(array_agg(g2id), ';') AS g2list,
array_to_string(array_agg(g3id),';') AS g3list, 
count(distinct g1id) AS g1count, count(distinct g2id) AS g2count, count(distinct g3id) AS g3count
INTO greg_list
FROM "GREG", priogrid_land WHERE ST_Intersects("GREG".the_geom, priogrid_land.cell)
GROUP BY priogrid_land.gid, priogrid_land.cell;</span></pre></div><br /><br />This will give this result:<br />g1list;
g2list;g3list; g1count; g2count; g3count<br />"482";"0";"0";1;1;1<br />"23;482;482";"0;0;0";"0;0;0";2;1;1<br />
"1227;482;23";"0;0;0";"0;0;0";3;1;1<br/>"1227;23;482;66";"0;0;0;0";"0;0;0;0";4;1;1<br
/>"1227;23;66";"0;0;0";"0;0;0";3;1;1<br/><br />As you see i.e. in g1list 482 is counted twice in row 2. 0 is also
counted.The distinct works for count, but not for array_agg.<br /><br />Cheers.</span> 

On Thu, Feb 17, 2011 at 6:20 AM, Andreas Forø Tollefsen
<andreasft@gmail.com> wrote:
> Hi all!
>
> I have tried the below query, but i cannot find a way to select only
> DISTINCT into the ARRAY_AGG function. I also do not want 0 to be included in
> the array or 0 to be counted.
>
> Code:
>
> SELECT priogrid_land.gid, priogrid_land.cell,
> array_to_string(array_agg(g1id), ';') AS g1list,
> array_to_string(array_agg(g2id), ';') AS g2list,
> array_to_string(array_agg(g3id), ';') AS g3list,
> count(distinct g1id) AS g1count, count(distinct g2id) AS g2count,
> count(distinct g3id) AS g3count
> INTO greg_list
> FROM "GREG", priogrid_land WHERE ST_Intersects("GREG".the_geom,
> priogrid_land.cell)
> GROUP BY priogrid_land.gid, priogrid_land.cell;
>
>
> As you see i.e. in g1list 482 is counted twice in row 2. 0 is also counted.
> The distinct works for count, but not for array_agg.
>

I don't have a version earlier than 8.4, but in 8.4+ you can use
DISTINCT in array_agg().
Eg.
array_to_string(array_agg(distinct g1id),';') as ...

On Thu, Feb 17, 2011 at 12:11 PM, Andreas Forø Tollefsen
<andreasft@gmail.com> wrote:
> Great. Thanks. Do you have a suggestion on how to ignore the group id's with
> 0 as value?
> I dont want these to be counted.

You can probably select your values in a subquery and filter out the 0
value results in the WHERE clause, then apply your existing query
(with distinct array_agg) to the outer query.
Or another way would be to use a CASE statement to skip the 0 values.
eg.
array_to_string(array_agg(distinct (case when g1id <> 0 then g1id end)
),';') ...

The array_to_string transformation should trim out the NULLs from the
CASE statement.