Select or boolean aggregate function in PostgreSQL

I would like to ask you how in PostgreSQL can you check if one of bo开发者_如何学编程olean values in table's column is true using select or aggregate function?

There are few boolean specific aggregate functions you may use: bool_and, bool_or, every.

In your particular case you need bool_or aggregate.
The query is as simple as this:

SELECT bool_or(my_column) FROM my_table

You can't use SUM(DATA) but you could cast the value (see below) to int (0=false, 1=true). However it may be more efficient to use EXISTS(...), specially if you are not interested in the number of TRUE values.

create table test(data boolean);
insert into test values(true), (false);
select sum(cast(data as int)) from test;
select exists(select * from test where data);

To know whether there is at least 1 true value:

select sum(cast(data as int)) > 0

This is better than the exists solution because it can be embedded into a larger query, maybe containing group by and other where clauses