Issue with Dynamic WHERE condition in Cursor in FUNCTION.

Question

Hi All,
I am facing an issue with cursor having dynamic WHERE condition in a function.
Below is the FUNCTION:
CREATE OR REPLACE FUNCTION EXCEPTION_MERGE(TABLE_NAME IN VARCHAR2, TAB_NAME IN VARCHAR2)
RETURN VARCHAr2
IS
stmt_tabcols VARCHAR2(32767);
v_columnname VARCHAR2(32767);
CURSOR C1 IS
SELECT 'A.'||A.COLUMN_NAME ||' = '|| 'B.'||B.COLUMN_NAME COLUMN_NAME
FROM
SELECT COLUMN_ID, COLUMN_NAME
FROM USER_TAB_COLUMNS
WHERE TABLE_NAME  = TABLE_NAME
AND COLUMN_NAME NOT IN ('ERROR_TAB_ID','ERROR_LOAD_DATE')
) A,
SELECT COLUMN_ID, COLUMN_NAME
FROM USER_TAB_COLUMNS
WHERE TABLE_NAME = TAB_NAME
) B
WHERE A.COLUMN_ID = B.COLUMN_ID;
BEGIN
FOR TABCOL IN C1
LOOP
    stmt_tabcols := stmt_tabcols ||TABCOL.COLUMN_NAME||',';
END LOOP;
    stmt_tabcols := RTRIM(stmt_tabcols, ',');
    RETURN stmt_tabcols;
END;
SELECT EXCEPTION_MERGE('WC_W_TEST_FS','WC_W_TEST_FS_GBL') FROM DUAL;It throws, below error:
ORA-06502 : PL/SQL : Numeric or value error : character string buffer too smallIf I REPLACE TABLE_NAME and TAB_NAME with hard coded values , it works fine. Can somebody look at the code and let me know the issue.
Edited by: ace_friends22 on Sep 9, 2012 1:08 PM

Answer 1

Etbin neatly demonstrating the value of posting code in a manner which makes it easy to read.
It's obviously an naming/scoping issue. Faced with a join like this:
where table_name = table_namethe engine looks for something called table_name in the current scope. It finds it, a column on USER_TAB_COLUMNS and applies it to both sides of the filter. It has no way of knowing that there is also a parameter called TABLE_NAME, because that is outside its current scope. Consequently the query will join every table in your schema regardless of what values you pass, and that's why you blow the buffer.
Takw etbin's advice and name your parameter with a prefix:
where table_name = p_table_nameThis isn't a column in USER_TAB_COLUMNS which will force the engine to look in the next scope up, which in your case is the function, where it will find your parameter and so generate a query for the passed values only.
Cheers, APC
Edited by: APC on Sep 9, 2012 8:03 AM