Topic: Database Administration >> synonyms
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| black |
Posted: Aug 24, 2007 03:38:00 AM |
Total Post: 14
Joined: Aug, 2007
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hi friends,
what is synonyms,views,sequence? pls explain me detail |
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 Mohammed Taj |
| Posted: Aug 24, 2007 08:06:04 AM |  |
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Total Post: 694
Joined: Jul, 2007
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synonym ---> exact copy of table and duplicate copy
view ----> image or window of tables
eg: view use for complex query...
you should create view for complex query which create through more than one tables.
sequence ---> unique number generator.
Regards
Taj
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| Nehru |
| Posted: Aug 24, 2007 08:17:36 AM | |
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Total Post: 43
Joined: Jul, 2007
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Hi,
Better to go this explanation:
SYNONYM:
If you aften are refers to tables of yours of maximum lenght/difficult names or other users it is useful to use a synonym instead of
user.table.
A synonym can be created using the command
"create synonym synonym_name for table_name/user.table_name;"
It is then possible to use simply synonym_name in a from clause.
Ex:
create synonym test for employeeinformation;
VIEW:
In Oracle the SQL command to create a view <virtual table> has the form
create or replace view <view_name> [(<column(s)>)] as
<select-statement> [with check option [constraint <name>]];
The optional clause or replace re creates the view if it already exists.
Ex:
create view DEPT20 as
select ENAME, JOB, SAL from EMP
where DEPTNO = 20;
A view can be used in the same way as a table. that is rows can be retrieved from a view
and also respective rows are not physically stored. A view is evaluated again each time it is
accessed, In Oracle SQL no insert, update, or delete modifications on views are allowed
SEQUENCE:
Sequence is used to insert number to the table,if the contains ID column which is Primary key, then better to use sequence
create sequence test_sequence start with 1 increment by 1;
then you can use like this
insert into test(testID,testname) values(test_sequence.NEXTVAL,'Exam');
I think after reading this you can under stand all above,
Any one let me know if am wrong.
Take Care
Bye
Nehru
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| black |
| Posted: Aug 27, 2007 12:44:04 AM | |
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Total Post: 14
Joined: Aug, 2007
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| Mohammed Taj |
| Posted: Aug 27, 2007 12:46:20 AM | |
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Total Post: 694
Joined: Jul, 2007
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You'r right Nehru ;-)
Regards
Taj
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