ORA-01788：此查询块中要求connect…

ORA-01788

Oracle Server - EnterpriseEdition - Version: 10.2.0.3
This problem can occur on anyplatform.
After upgrading to Oracle 10g,started getting an ORA-1788 error for a query that includes theLEVEL pseudo column. This query was running fine on9i.

Example:

On 9i:

SQL> select level fromdual;

LEVEL
----------
0

On 10g:

SQL> select level fromdual;
select level from dual
*
ERROR at line 1:
ORA-01788: CONNECT BY clause requiredin this query block

Solution:

SQL> alter system set"_allow_level_without_connect_by"=truescope=spfile;

or if using a pfile add theline

_allow_level_without_connect_by=true

at the beginning of thepfile.