undocumented parameter

Just in case you read my success story on Don Burleson webpage about undocumented parameters. out of metalink thread 460157.996 : “I set appropriate values for pga_aggregate_target and _pga_max_size… alter system set pga_aggregate_target=6G; alter system set “_pga_max_size”=2000000000; …and I gave the query some hints “NOREWRITE FULL USE_HASH ORDERED”. As a result, it boosted my query […]

select column only if it exists

i need to display tablespace attributes SQL> select tablespace_name, status, contents, logging, extent_management, allocation_type, segment_space_management, retention, bigfile from dba_tablespaces; TABLESPACE_NAME STATUS CONTENTS LOGGING EXTENT_MAN ALLOCATIO SEGMEN RETENTION BIG ——————– ——— ——— ——— ———- ——— —— ———– — SYSTEM ONLINE PERMANENT LOGGING LOCAL SYSTEM MANUAL NOT APPLY NO looks fine. but what if I try that […]

exotic constraints

Today I read a post on metalink where the user wanted a unique constraint for not-null values… Sounds easy, because Oracle never indexes null in btree index. If I have only one column, I simply index it, it will work. SQL> create table t66 ( n number); Table created. SQL> create unique index i66 on […]