Question { Perot Systems, 18185 }
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 ?
Answer
10) Null is not equal to "" or 0. it is un identified value
means suppose there is column Phone number.
If we do not any phone number we can insert NULL.
"" means empty String.
Select * from table where roll=""(EMPTY)
select * from table where roll is NULL(UNDEFINED)
2) Correct Answer.
View is made up of base tables. Suppose we select data from
two table table1 & table2 ,these are base tables.
He wants to ask u if we drop a table table2,Will view give
error.
Yes.But if we recreate the table we can query the view
again.
Try it by urself--
First create the view by selecting the data from two tables
then select columns from view
Suppose select * from view1
then drop one of the tables
then select * from view1 gives error.
12) NO.
13) ENTITY INTEGRITY--We cannit insert null in a parimary
key. CZ if two columns have tha value we cannot distinguish
b/w two rows.
REFERENTIAL INTEGRITY---Vales in foregn key table are only
those that match a value in a primary key table.
DOMAIN CONSTRAINT--A unique value for a column.
Exampl--Empid