because the function didn't exist in 7.4.X.
-
+
Applications may use this to determine the version of the database server they
are connected to. The number is formed by converting the major, minor, and
revision numbers into two-decimal-digit numbers and appending them
-together. For example, version 7.4.2 will be returned as 70402, and version
+together. For example, version 8.1.5 will be returned as 80105, and version
8.1 will be returned as 80100 (leading zeroes are not shown). Zero is
returned if the connection is bad.