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Oh, I haven't worked with databases. Hermit, my question is, is the entire integer part of the number fully utilized, for all 20 digits? If there's some room for improvement, you could store additional fractional digits in the integer part. By the way, this would only require one digit: for example, you could use the very first digit to indicate how many digits from the fractional part are carried over to the integer part (0-9, nine should be enough), and then use the remaining digits for the actual digits, whether they are integer or fractional, depending on... In total, this would use 19+4=23 digits for the integer and fractional parts of the number, with the fractional part having up to 13 digits. But honestly, this is just a workaround.
P.S. By the way, I just invented a floating-point number; I'm a genius, to hell with all of you!