pgsql-bugs(at)postgresql(dot)org writes:
> M_ID VARCHAR(10) M_DESC VARCHAR(10)
> -----------------------------------------------------------
> ABC HELLO
> UPDATE MYTABLE SET M_DESC='GOOD' WHERE M_ID='ABC ' AND M_DESC='HELLO '
> UPDATE 0 RECORDS
My guess is that the stored values do not have trailing spaces.
Trailing spaces are significant data in varchar fields.
regards, tom lane