SELECT owner, table_name
FROM dba_tables
This is assuming that you have access to the DBA_TABLES data dictionary view. If you do not have those privileges but need them, you can request that the DBA explicitly grants you privileges on that table, or, that the DBA grants you the SELECT ANY DICTIONARY privilege or the SELECT_CATALOG_ROLE role (either of which would allow you to query any data dictionary table). Of course, you may want to exclude certain schemas like SYS and SYSTEM which have large numbers of Oracle tables that you probably don't care about.
Alternatively, if you do not have access to DBA_TABLES, you can see all the tables that your account has access to through the ALL_TABLES view:
SELECT owner, table_name
FROM all_tables
Although, that may be a subset of the tables available in the database (ALL_TABLES shows you the information for all the tables that your user has been granted access to).
If you are only concerned with the tables that you own, not those that you have access to, you could use USER_TABLES:
SELECT table_name
FROM user_tables
Since USER_TABLES only has information about the tables that you own, it does not have an OWNER column – the owner, by definition, is you.
Oracle also has a number of legacy data dictionary views-- TAB, DICT, TABS, and CAT for example-- that could be used. In general, I would not suggest using these legacy views unless you absolutely need to backport your scripts to Oracle 6. Oracle has not changed these views in a long time so they often have problems with newer types of objects. For example, the TAB and CAT views both show information about tables that are in the user's recycle bin while the [DBA|ALL|USER]_TABLES views all filter those out. CAT also shows information about materialized view logs with a TABLE_TYPE of "TABLE" which is unlikely to be what you really want. DICT combines tables and synonyms and doesn't tell you who owns the object.
You can use a subquery for this like
select *
from
( select *
from emp
order by sal desc )
where ROWNUM <= 5;
Have also a look at the topic On ROWNUM and limiting results at Oracle/AskTom for more information.
Update:
To limit the result with both lower and upper bounds things get a bit more bloated with
select * from
( select a.*, ROWNUM rnum from
( <your_query_goes_here, with order by> ) a
where ROWNUM <= :MAX_ROW_TO_FETCH )
where rnum >= :MIN_ROW_TO_FETCH;
(Copied from specified AskTom-article)
Update 2:
Starting with Oracle 12c (12.1) there is a syntax available to limit rows or start at offsets.
SELECT *
FROM sometable
ORDER BY name
OFFSET 20 ROWS FETCH NEXT 10 ROWS ONLY;
See this answer for more examples. Thanks to Krumia for the hint.
Best Answer
The
PARTITION BYclause sets the range of records that will be used for each "GROUP" within theOVERclause.In your example SQL,
DEPT_COUNTwill return the number of employees within that department for every employee record. (It is as if you're de-nomalising theemptable; you still return every record in theemptable.)If there was another column (e.g.,
state) then you could count how many departments in that State.It is like getting the results of a
GROUP BY(SUM,AVG, etc.) without the aggregating the result set (i.e. removing matching records).It is useful when you use the
LAST OVERorMIN OVERfunctions to get, for example, the lowest and highest salary in the department and then use that in a calculation against this records salary without a sub select, which is much faster.Read the linked AskTom article for further details.