The following bug has been logged online:

Bug reference: 1171
Logged by: Harro Lock

Email address: harro1 (AT) dataleaf (DOT) nl

PostgreSQL version: 7.4

Operating system: Linux

Description: select distinct 'value',... fails.

Details:

'select distinct' fails when using a string value in the columnlist.

Here is a minimal query that reproduces the bug:

select distinct 'value';

This should give "value" as a result, but it produces this error-message:

ERROR: Unable to identify an ordering operator '<' for type '"unknown"'
Use an explicit ordering operator or modify the query


A work-around for this bug is to cast the string to a known type:

select distinct cast('value' as varchar);



---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings

"PostgreSQL Bugs List" <pgsql-bugs (AT) postgresql (DOT) org> writes:
This is accepted in 7.4 and later. You are evidently using something
older.

regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 2: you can get off all lists at once with the unregister command
(send "unregister YourEmailAddressHere" to majordomo (AT) postgresql (DOT) org)