Computer Tutorials
Earn Money From Internet
Cheap Freelancers
Ask An Expert
Register Cheap Domain
Data Recovery
Best Mutual Funds
Trading Forex Online
Cheap Web Hosting
Ajax Tutorials
Cheap Cell Phone Plans
Free Mobile Learning
Job Portal
Photoshop Tutorials
Cheap Jewelry
Cheapest Air Travel
Oracle Interview Questions And Answers
|
Page 30 of 95
SQL PLUS STATEMENTS 1. What are the types of SQL Statement ? Data Definition Language : CREATE,ALTER,DROP,TRUNCATE,REVOKE,NO AUDIT & COMMIT. Data Manipulation Language : INSERT,UPDATE,DELETE,LOCK TABLE,EXPLAIN PLAN & SELECT. Transactional Control : COMMIT & ROLLBACK Session Control : ALTERSESSION & SET ROLE System Control : ALTER SYSTEM. 2. What is a transaction ? Transaction is logical unit between two commits and commit and rollback. 3. 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 TRUNCATE DELETE allows the filtered deletion. Deleted records can be rolled back or committed. Database triggers fire on DELETE. 4. What is a join ? Explain the different types of joins ? Join is a query which retrieves related columns or rows from multiple tables. Self Join - Joining the table with itself. Equi Join - Joining two tables by equating two common columns. Non-Equi Join - Joining two tables by equating two common columns. Outer Join - Joining two tables in such a way that query can also retrive rows that do not have corresponding join value in the other table. 5. What is the Subquery ? Subquery is a query whose return values are used in filtering conditions of the main query. 6. What is correlated sub-query ? Correlated sub_query is a sub_query which has reference to the main query. 7. Explain Connect by Prior ? Retrives rows in hierarchical order. e.g. select empno, ename from emp where. 8. Difference between SUBSTR and INSTR ? INSTR (String1,String2(n,(m)), |