DBA Tips Archive for Oracle
Understanding Maximum Sizes for VARCHAR2 Data
by Jeff Hunter, Sr. Database Administrator
Oracle provides the ability in both SQL and PL/SQL to work with the VARCHAR2 data type. However, they differ in their maximum allowed length. Within PL/SQL, local variables of type VARCHAR2 can be declared to contain up to 32,767 characters while declaring a database column of type VARCHAR2 can contain up to 4000 characters.
This SQL VARCHAR2 limit of 4000 characters exists even when VARCHAR2 values appear inside DML statements like SELECT, INSERT, UPDATE and DELETE.
When referencing PL/SQL functions inside DML statements, ensure the return value does not exceed 4000 characters.
The example below illustrates the problem when referencing PL/SQL functions inside DML statements:CREATE OR REPLACE FUNCTION starcount(number_of_stars NUMBER) RETURN VARCHAR2 IS BEGIN RETURN RPAD('*',number_of_stars,'*'); END; /
The statement:select starcount(4000) from dual;would select and display 4000 stars while the statement:select starcount(4001) from dual;would produce the following error:select starcount(4001) from dual * ERROR at line 1: ORA-06502: PL/SQL: numeric or value error: character string buffer too small ORA-06512: at line 1
If you require to work with character data greater than 4K, use the CLOB data type and the DBMS_LOB package.
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