Question

I’m trying to create a user defined function in Oracle that will return a DATE when given a text argument containing a date substring. I’ve tried a couple ways of writing this, and all seem to throw the same error:

CREATE OR REPLACE FUNCTION lm_date_convert (lm_date_in IN VARCHAR2(50))
  RETURN DATE DETERMINISTIC IS
BEGIN
  RETURN(TO_DATE(REGEXP_REPLACE(lm_date_in, '([[:digit:]]{2})[-/.]*([[:digit:]]{2})[-/.]*([[:digit:]]{4})','\3-\1-\2'), 'YYYY-MM-DD'));
END;

the error:

FUNCTION lm_date_convert Compiled. 1/46
PLS-00103: Encountered
the symbol “(” when expecting one of
the following:

:= . ) , @ % default character The
symbol “:=” was substituted for “(” to
continue.

Any thoughts on this, and general UDF writing tips (and good references) are welcome! Thanks.

Answer 1

We cannot restrict the datatype when specifying parameters in stored procedures. That is, just use VARCHAR2 rather than VARCHAR2(50).

Just to prove I’m reproducing your problem …

SQL> CREATE OR REPLACE FUNCTION lm_date_convert (lm_date_in IN VARCHAR2(50))
  2    RETURN DATE DETERMINISTIC IS
  3  BEGIN
  4    RETURN(TO_DATE(REGEXP_REPLACE(lm_date_in, '([[:digit:]]{2})[-/.]*([[:digit:]]{2})[-/.]*([[:digit:]]{4})','\3-\1-\2'), 'YYYY-MM-DD'));
  5  END;
  6  /

Warning: Function created with compilation errors.

SQL> sho err
Errors for FUNCTION LM_DATE_CONVERT:

LINE/COL ERROR
-------- -----------------------------------------------------------------
1/49     PLS-00103: Encountered the symbol "(" when expecting one of the
         following:
         := . ) , @ % default character
         The symbol ":=" was substituted for "(" to continue.

SQL>

Now to fix it:

SQL> ed
Wrote file afiedt.buf

  1  CREATE OR REPLACE FUNCTION lm_date_convert (lm_date_in IN VARCHAR2)
  2    RETURN DATE DETERMINISTIC IS
  3  BEGIN
  4    RETURN(TO_DATE(REGEXP_REPLACE(lm_date_in, '([[:digit:]]{2})[-/.]*([[:digit:]]{2})[-/.]*([[:digit:]]{4})','\3-\1-\2'), 'YYYY-MM-DD'));
  5* END;
SQL> r
  1  CREATE OR REPLACE FUNCTION lm_date_convert (lm_date_in IN VARCHAR2)
  2    RETURN DATE DETERMINISTIC IS
  3  BEGIN
  4    RETURN(TO_DATE(REGEXP_REPLACE(lm_date_in, '([[:digit:]]{2})[-/.]*([[:digit:]]{2})[-/.]*([[:digit:]]{4})','\3-\1-\2'), 'YYYY-MM-DD'));
  5* END;

Function created.

SQL> 

---

“If you really do want a VARCHAR2(50)
then declare a type of VARCHAR2(50)
and use the type.”

Declaring a SQL TYPE to enforce sizing is a bit of overkill. We can declare SUBTYPEs in PL/SQL but their sizes are not actually enforced in stored procedure signatures. However there are workarounds as I discuss in this other thread.

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As an aside, why are you using Regex to solve this problem? Or rather, what problem are you trying to solve which cannot be solved with TO_CHAR and TO_DATE? Oracle’s pretty forgiving with format masks.