Many PL/SQL developers are unaware of the STANDARD package, and its implications for their PL/SQL code. For example, it is common to find programmers who assume that names like INTEGER and TO_CHAR are reserved words in the PL/SQL language. That is not the case. They are, respectively, a datatype and a function declared in the STANDARD package.

STANDARD is one of the two default packages of PL/SQL (the other is DBMS_STANDARD). Because STANDARD is a default package, you do not need to qualify references to datatypes like INTEGER, NUMBER, PLS_INTEGER, etc., with “STANDARD”—but you could, if you so desired.

PLW-5004 notifies you if you happen to have declared an identifier with the same name as an element in STANDARD (or a SQL built-in; most built-ins—but not all—are declared in STANDARD).

Consider this procedure definition:

  1  CREATE OR REPLACE PROCEDURE plw500 4
  2  IS
  3     INTEGER   NUMBER;
  4
  5     PROCEDURE TO_CHA R
  6     IS
  7     BEGIN
  8        INTEGER := 10;
  9     END TO_CHAR;
 10  BEGIN
 11     TO_CHAR;
 12  * END plw5004;

Compile-time warnings for this procedure will display as follows:

  LINE/COL ERROR 
  -------- ---------------------------------
  3/4      PLW-05004: identifier INTEGER is
           also declared in STANDARD or is a
           SQL builtin
  5/14     PLW-05004: identifier TO_CHAR is
           also declared in STANDARD or is a
           SQL builtin

You should avoid reusing the names of elements defined in the STANDARD pack age unless you have a very specific reason to do so.