Oracle 9i: Supposedly missing right parenthesis
Question
I have a simple function written in Oracle 9i (version 9.2.0.4.0) to simulate an in-line IF. For those interested, here's the code:
create or replace
FUNCTION IIF
(testExpression NUMBER,
trueResult NUMBER,
falseResult NUMBER)
RETURN NUMBER
AS
BEGIN
/*
A simple in-line IF function for use with SQL queries. If the test
expression evaluates to any non-zero value, it is considered to be
true, and the trueResult is returned. Otherwise, falseResult is
returned.
*/
IF (testExpression is null) or (testExpression = 0) THEN
return falseResult;
ELSE
return trueResult;
END IF;
END IIF;
This isn't rocket science. Now, here's the big mystery: if I execute the following SQL statements, everything is just fine, and works exactly as I expect:
SELECT IIF(1, 'true', 'false') FROM DUAL;
SELECT IIF(0, 'false', 'true') FROM DUAL;
However, the following generates a really bizarre error from Oracle:
SELECT IIF((0 = 1), 'false', 'true') FROM DUAL;
That error is as follows:
ORA-00907: missing right parenthesis.
Clearly, that isn't the case. Would anyone happen to have an explanation for this little bit of bizarreness?
It's taking a whole lot of self-control at the moment to restrain myself from hurling the Oracle server out the window. Oracle seems rife with these kinds of inanities.
EDIT: Is there some kind of magic syntax I have to use to use an equality operator in a select statement?
Solution
Maybe you can explain what you are trying to do. I think you are looking for the CASE
or DECODE
functions, but I can't be sure. It seems like you are working against the grain of the SQL language for some reason.
The error occurs because Oracle doesn't expect a relational operator in the select
clause of the query:
SQL> SELECT IIF(1>7, 0, 1) FROM DUAL;
SELECT IIF(1>7, 0, 1) FROM DUAL
*
ERROR at line 1:
ORA-00907: missing right parenthesis
SQL> SELECT 1=0 FROM DUAL;
SELECT 1=0 FROM DUAL
*
ERROR at line 1:
ORA-00923: FROM keyword not found where expected
See this Ask Tom article.
OTHER TIPS
You want
SELECT CASE WHEN *expr* then 'true' else 'false' end col_alias FROM DUAL;
or for simple equality test
SELECT DECODE(*val1*,*val2*,'true','false') col_alias FROM dual;
This will perform much better than dropping out to a PL/SQL function. There's a number of reasons why your approach doesn't work.
Booleans aren't an Oracle data type.
They are a PL/SQL datatype, but even then there's no implicit conversion to numbers (zero false, non-zero true)
There's no 'expression' datatype, so the SQL engine can't pass the expression to PL/SQL.
Even if you passes the expression as a string to PL/SQL, the PL/SQL engine cannot dynamically evaluate an expression in a string. It would have to build the string into a dynamic SQL statement and execute that dynamically, returning a result (in a valid SQL datatype, like a string or number).
- There is no BOOLEAN type in the Oracle database, so you can't use an expression like "(1=0)".
- Even if there were a BOOLEAN type, you have declared the first argument to be of type NUMBER. You have to pass it a number, or something that can be implicitly converted to one.
- Finally, I don't understand how any of your examples actually produced anything besides "invalid number", since your second and third arguments can't be converted to numbers, either.
Having never worked with oracle I can't directly offer any sound advice, but looking at the statement it could be oracle having a problem inferring number from boolean?..
The IIF signature is expecting a NUMBER as the first argument and in the call you are passing a BOOL evaluation.
This is just a thought.
Besides decode and case, there is also nvl.