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1. What are the grouping function in SQL ?
2. If base table of a view deleted means, what will happen
while we querying on view ? will give any error ?
3. Difference between DROP, DELETE, TRUNCATE table ?
4. What is constraints and types ?
5. What is max size of nchar & nvarchar ?
6. Define ROLLBACK, COMMIT, SAVE POINT
7. How non-clustered better ? or rank the Clustered,
Non-Clustered and Table scan in performance wise
8. Select 10 rows from a table ?
9. Define DML, DDL, DCL, DTL commands ?
10. What is mean by NULL value ? NULL means "" or 0 or
undefined ?
11. Default constraints ?
12. Can we have more then primary Key in table ?
13. Type of integrity ? Entity, Referential, Domain ?
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Answer Posted / srivas
What is the difference between DROP,DELETE,TRUNCATE table ?
Delete:It's an DML command which is used for deleting
particular table in the database...even though we delete the
data we can regain it by rollback command.
Example:SQL> SELECT COUNT(*) FROM emp;
COUNT(*)
----------
14
SQL> DELESQL> SELECT COUNT(*) FROM emp;
COUNT(*)
----------
14
SQL> DELETE FROM emp WHERE job = 'CLERK';
4 rows deleted.
SQL> COMMIT;
Commit complete.
Truncate:This command is a DDL Command which is used to
delete a table...I Just Conclude it as
Truncate=Delete+Commit...once u applied this on table u
can't get the data back...but the structure will be there..
Example:
SQL> TRUNCATE TABLE emp;
Table truncated.
SQL> SELECT COUNT(*) FROM emp;
COUNT(*)
----------
0
Drop:It is used to destroy entire structure of a
table...once we apply this command on any particular table
we can't get it in anyway...so be cautious while applying
this command.
Example:
SQL> DROP TABLE emp;
Table dropped.
SQL> SELECT * FROM emp;
SELECT * FROM emp
*
ERROR at line 1:
ORA-00942: table or view does not exist
| Is This Answer Correct ? | 11 Yes | 3 No |
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