what is the difference between the query and corelated
query
- 8 Answers
- 18541 Views
- HSBC, IBM, TCS, Xenosoft, I also Faced
- E-Mail Answers
Answer Posted / lova raju allumalla
when performing joins on two or more tables, we normally
write a query making use relational operators such as =
etc. which means each and every row of every table is
compared with each other,which is a unwanted situation when
looked in the perspective performance issue. where as
making use of corelated query one can minimise the tedoius
checks as described above. consider the example below with
a normal join
select * from emp e,dept d where e.deptno=d.deptno;
now the above same can be performed by using the co related
query
select * from emp where deptno in (select deptno from dept);
u can now make up the difference, in the first approach in
emp table, each row deptno value compared for each row
deptno value of dept table.where as in second approach the
(select deptno from dept) is executed only once for all
checks of the outer query select * from emp where deptno
| Is This Answer Correct ? | 0 Yes | 0 No |
Post New Answer View All Answers
What are all the different normalization?
Where not exists in sql?
Explain foreign key in sql?
What is t sql used for?
What is crud sql?
What is dense_rank in sql?
How many columns should be in an index?
What is the use of sqldataadapter?
What is where clause in sql?
Explain the savepoint statement.
What is difference between function and trigger?
what happens if null values are involved in expressions? : Sql dba
Can we use threading in pl/sql?
What is full form of rtm?
Which constraints we can use while creating database in sql?
