pls answer this??

[Grishma Dube]

Can anyone answer this??
1. Locking is used to ensure --- Database
a. Transaction control
b. Multi threading
c. Safety
d. Concurrent �read� operations
2. What is primary key? ---- Database
a. Used to identify each row uniquely
b. It is always unique and not null
c. It is rarely modified
d. All of the above
3. Join operation can be performed on --- Database
a. One or more tables
b. 2 or more tables
c. only tables but not views
d. one or more views or tables
4. Join operation works faster --- Database
a. With fewer columns
b. When properly indexed
Thanx in adv

[sachin kumar Kansal]

hi Grishma !
probable anwsers are
1. a
2. a
3. d
4. a in case data is more
b in case data is less
i hope they r correct

[Francis Siu]

1. Locking is used to ensure --- Database
a. Transaction control
I think it avoids mutating
2. What is primary key? ---- Database
d. All of the above
a is correct
b correct too
c is right because it can modify but rarely
so d is the answer.
3. Join operation can be performed on --- Database
b. 2 or more tables
Actually, the best method is test it.
4. Join operation works faster --- Database
a. With fewer columns
b. When properly indexed
I think that it depends on which situation. Both are correct.
[ March 17, 2004: Message edited by: siu chung man ]