Please clarify these doubts

Question

1.From 10g onwards, oracle introduced new data types BINARY_FLOAT and BINARY_DOUBLE.What is the significance of word BINARY in these datatypes?
Is the word BINARY because of the way the calculations are done when these datatypes are used?
2.*Oracle uses blank characters to fill format elements to a constant width equal to the largest element for the relevant format model in the current*
session language.What is the reason for returning constant width?
3.In the syntax for simple comparison conditions, the syntax when we have more than one expression is
*(expr1,expr2,...) {=| != | ^= | <>} (subquery)*.My question here is why other relational operators like <,>,<= and >= are not allowed?Is there any specific reason for this?
Regards,
Sreekanth Munagala

Answer 1

Hi, Sreekanth,
Sreekanth Munagala wrote:
... My question was how Oracle treats a string literal in SQL functions, whether it treats it as a CHAR or VARCHAR2 datatype?"String literal" means text enclosed in single-quotes. For example, the 2nd argument in this call to TO_CHAR is a string literal:
TO_CHAR ( hiredate     -- This argument is a DATE column
     , 'DD-Mon-YYYY'     -- This argument is a string literal
     )What does it matter if the string literal is treated as a CHAR or a VARCHAR2? Give a specific example.
You can see the data types of arguments by querying the data dictionary view all_arguments. There are several versions of TO_CHAR, overloaded in the package sys.standard. You'll see that many of them have the data type VARCHAR2, but none of them have the data type CHAR. If you do pass a CHAR argumnent where the function is expecting a VARCHAR2, it will implicitly convert it.
Since CHAR is a fixed length datatype and the output of the function TO_CHAR is always a fixed length by default (i.e. without using FM), i think oracle is treating the string literal as CHAR datatype.Are you talking about the value returned by the function, or some literal? Literals only apply to written code; functions never return literals.
The output of the function TO_CHAR is not always a fixed length without 'FM'. For example, this one call to TO_CHAR in one query, using one set of NLS settings:
SELECT  TO_CHAR (comm, 'TM')  AS f_comm
FROM    scott.emp;produces strings that are sometimes 1 character long, sometimes 3, and sometimes 4, as well as NULLs.
It may be true that a given call to TO_CHAR in a given statement, where the first argument is a DATE and the 2nd argument is a constant and does not include 'FM', will always return a string of the same length. That still doesn't matter. The return type of the function has to be specified when the function is compiled; the system can't wait until you call the function, then examine its arguments to see if they meet all the special conditions set above, and only then determine which data type to return. It has to know, before the function is ever used, which data type to return.
Look up TO_CHAR in the SQL Language manual to see what data type it returns. It's VARCHAR2.