Plz help to write a function

Question

i want to create a function in which whenever i used
isnull(cloumn_name,' ')<>' ' i want to invoke the function
nvl(column_name,' ')<>' '
eg- select * from table_name where isnull(cloumn_name,' ')<> ' ' should return the same output as
select * from table_name where nvl(cloumn_name,' ')<> ' '
plese help mee urgent

Answer 1

Here's code for a function that you can use for any column of any table. Beware of the SQL intejection, however. Modify the code to avoid this problem.
SQL> CREATE OR REPLACE FUNCTION get_nulls(p_table varchar2,p_column varchar2,p_rowid rowid)
  2    RETURN number IS
  3    v_cnt number;
  4  BEGIN
  5    EXECUTE IMMEDIATE ('SELECT COUNT(*) FROM '||p_table||' WHERE '||p_column||
  6       ' IS NULL AND ROWID='''||p_rowid||'''') INTO v_cnt;
  7    RETURN v_cnt;
  8  END;
  9  /
Function created.
  1  CREATE TABLE test
  2  (col1 varchar2(10),
  3  col2 varchar2(10),
  4* col3 varchar2(15))
SQL> /
Table created.
SQL> INSERT INTO test
  2  VALUES('AAA','BBB',NULL)
  3  /
1 row created.
SQL> INSERT INTO test
  2  VALUES('CCC',NULL,'DDD')
  3  /
1 row created.
SQL> INSERT INTO test
  2  VALUES(NULL,'EEE','FFF')
  3  /
1 row created.
SQL> SELECT * FROM test;
COL1       COL2       COL3
AAA        BBB
CCC                   DDD
           EEE        FFF
SQL> SET FEEDBACK 3
SQL> SELECT * FROM test;
COL1       COL2       COL3
AAA        BBB
CCC                   DDD
           EEE        FFF
3 rows selected.
SQL> ED
Wrote file afiedt.buf
  1  SELECT *
  2  FROM test
  3* WHERE get_nulls('TEST','COL1',ROWID)>0
SQL> /
COL1       COL2       COL3
           EEE        FFF
SQL> ED
Wrote file afiedt.buf
  1  SELECT *
  2  FROM test
  3* WHERE get_nulls('TEST','COL2',ROWID)>0
SQL> /
COL1       COL2       COL3
CCC                   DDDAnwar