Clarify SQL type assignment for numeric literals [HZ-1748] (#800)

* Clarify SQL type assignment for numeric literals [HZ-1748]

* Minor edits.

---------

Co-authored-by: Serdar Ozmen <[email protected]>

docs/modules/sql/pages/data-types.adoc

@@ -75,4 +75,16 @@
 
 == Casting and Data Type Conversion
 
-To convert one data type to another (also known as casting), you can use the xref:functions-and-operators.adoc#cast[`CAST(expression AS type_name)`] function.
+To convert one data type to another (also known as casting), you can use the xref:functions-and-operators.adoc#cast[`CAST(expression AS type_name)`] function.
+
+== Numeric Literals
+
+When numeric literals are assigned SQL types:
+
+. Integers, e.g., 1 and 42, receive the narrowest possible among `TINYINT`, `SMALLINT`, `INTEGER`, `BIGINT` and `DECIMAL`.
+. Floating-point numbers, e.g., 1.2 and 4.2, receive `DECIMAL`.
+. Scientific notation (exponential form), e.g., 1e1 or 4.2e2, receives `DOUBLE`.
+
+As you realized, integers are optimized for storage, whereas floating-point numbers are not subject to such optimization. This is because `REAL` and `DOUBLE` cannot exactly represent all decimal numbers (see link:https://en.wikipedia.org/wiki/IEEE_754[IEEE 754]), and exactness cannot be compromised for financial applications. Finally, because of its rare usage, scientific notation is not optimized for storage, i.e., not tried to narrow to `REAL`.
+
+Numbers that are represented in scientific notation and out of range for `DOUBLE` will cause overflow and be interpreted as ∞ or -∞. For example, 1.8e+308 is greater than the largest possible finite value of `DOUBLE`, which is 1.7976931348623157e+308, and so it is only valid in the form 18000...0.