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ORACLE Interview Questions and Answers

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554. How do you find the numbert of rows in a Table ?

A bad answer is count them (SELECT COUNT(*) FROM table_name)
A good answer is :-
'By generating SQL to ANALYZE TABLE table_name COUNT STATISTICS by querying Oracle System Catalogues (e.g. USER_TABLES or ALL_TABLES).
The best answer is to refer to the utility which Oracle released which makes it unnecessary to do ANALYZE TABLE for each Table individually.


555. What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?

1,000,00


556. What are cursor attributes?

-%ROWCOUNT
-%NOTFOUND
-%FOUND
-%ISOPEN


557. There is a % sign in one field of a column. What will be the query to find it?

'' Should be used before '%'.


558. What is ON DELETE CASCADE ?

When ON DELETE CASCADE is specified ORACLE maintains referential integrity by automatically removing dependent foreign key values if a referenced primary or unique key value is removed.


559. What is the fastest way of accessing a row in a table ?

Using ROWID.CONSTRAINTS


560. What is difference between TRUNCATE & DELETE ?

TRUNCATE commits after deleting entire table i.e., can not be rolled back. Database triggers do not fire on TRUNCATEDELETE allows the filtered deletion. Deleted records can be rolled back or committed.Database triggers fire on DELETE.


561. What is a transaction ?

Transaction is logical unit between two commits and commit and rollback.


562. What are the advantages of VIEW ?

To protect some of the columns of a table from other users.To hide complexity of a query.To hide complexity of calculations.


563. How will you a activate/deactivate integrity constraints ?

The integrity constraints can be enabled or disabled by ALTER TABLE ENABLE constraint/DISABLE constraint.


564. Where the integrity constraints are stored in Data Dictionary ?

The integrity constraints are stored in USER_CONSTRAINTS.


565. What is the Subquery ?

Sub query is a query whose return values are used in filtering conditions of the main query.

(Continued on next part...)

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ORACLE Interview Questions and Answers