Hello,
I'd like to create a function called count_bool(
column_name, boolean ) in PostgreSQL.
this function is similar to the count( column_name
) function but will only count the trues or falses based on the other input parameter
boolean. e.g. if you pass in a 'true', all the trues will be counted but not
the falses -- it's the same but opposite if the 'false' was passed in.
I’d like this aggregate function to be
developed with the SQL language instead of ‘C’ (for maintenance
reasons). From the surface, it appears to be an
incredibly simple job only to find that it's difficult.
In some respects, I can't believe this function
doesn't exist in SQL
so now I can create the statement
select distict product_id, count_bool(purchased,
true), count_bool(was_selected, true) from some_table group by product_id;
instead of breaking the query into 3 seperate
queries
select distict product_id from some_table;
select count(purchased) from product_id where
purchased = true;
select count(was_selected) from some_table where
was_selected = true;
Am I missing a detail with SQL based aggregate
function development?
Any help would be appreciated.
Thanks!
