Shouldn't binary_double store a higher value than number in Oracle?

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Considering the following test code :

CREATE TABLE binary_test (bin_float BINARY_FLOAT, bin_double BINARY_DOUBLE, NUM NUMBER);
INSERT INTO binary_test VALUES (4356267548.32345E+100, 4356267548.32345E+2+300, 4356267548.32345E+100);
SELECT CASE WHEN bin_double>to_binary_double(num) THEN 'Greater'
            WHEN bin_double=to_binary_double(num) THEN 'Equal'
            WHEN bin_double<to_binary_double(num) THEN 'Lower'
            ELSE 'Unknown' END comparison,
            A.*
FROM binary_test A;

I've tried to see which one stores higher values. If I try to add E+300 for the number and binary_float columns, it returns numeric overflow error. So, I thought I could store a greater value with the binary_float. However, when I tried to check it, it shows a lower value, and with the case comparison it says it is lower too. Could you please elaborate this situation?

oracle19c oracle sql
1 Answers

You are inserting the value 4356267548.32345E+2+300 into the binary double column. That evaluates to 4356267548.32345E+2, which is 435626754832.345, plus 300 - which is 435626755132.345 (or 4.35626755132345E+011, which becomes 4.3562675513234497E+011 when converted to binary double). That is clearly lower than 4356267548.32345E+100 (or 4.35626754832345E+109, which becomes 4.3562675483234496E+109 when converted to binary double).

Not directly relevant, but you should also be aware that you're providing a decimal number literal, which will be implicitly converted to binary double during insert. So you can't use 4356267548.32345E+300, as that is too large for the number data type. If you want to specify a binary double literal then you need to append a d to it, i.e. 4356267548.32345E+300d; but that is still too large.

The highest you can go with that numeric part is 4356267548.32345E+298d, which evaluates to 4.3562675483234498E+307 - just below the data type limit of 1.79769313486231E+308; and note the loss of precision.

db<>fiddle

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