=?GBK?B?w6vDqw==?= <krave@xxxxxxx> writes: > Do we have a rule by follow which one can accurately info the output of a SELECT statment FROM a table with floating-point data type? The goal of our floating-point output functions is to produce the shortest representation from which the stored value could be recovered exactly. It's not unusual for that to require two or three decimal digits more than the nominal precision. Keep in mind that the nominal precision, such as 6 digits for float4, is a *lower bound* on the number of decimal digits that will be stored accurately, whereas supporting exact round-trip I/O requires an *upper bound* number of digits. In short, no, there is not a trivial way to predict the number of digits emitted. If you have a problem with that, maybe you should be using type numeric instead. You can find more info by looking around for info about the Ryū float output algorithm, eg here: https://github.com/ulfjack/ryu regards, tom lane
