On Sat, Sep 17, 2005 at 04:00:50AM +0100, Pablo Oses wrote: > select cast(123.456::float4 as float8) > > what do you think its the answer ? 123.456 ? > > well pgsql 7.2.2, 8.0.0, 8.0.1 and 8.0.3 (all i have used) answers this: > 123.456001281738 which is WRONG
Float4 has a precision of only about 6 digits, so you can't assume much about the digits beyond that. See the documentation for floating-point types: http://www.postgresql.org/docs/8.0/interactive/datatype.html#DATATYPE-FLOAT This is hardly a behavior unique to PostgreSQL; use a search engine to find explanations of the problems of using binary floating-point numbers. If you need exact results then use the numeric type. -- Michael Fuhr ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
