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SQL Basics: Join


Monalisa Singh said…
Hello sir,
In this query,
select e.empno,e.ename,d.loc from emp e join dept d ON(e.deptno=d.deptno);

Here wat is the use of 'ON' clause, sir???

Monalisa Singh said…
wats r the queries 4 these questions sir:-

Q1.List the employees whose 10% of salary is equal to year of joining.

Q2.List the Mgrs who r senior to King & who are junior to Smith.
Mithun Ashok said…
Hi Mona,

On Caluse is used to,

1. To specify arbitrary conditions or specify columns to join.
2. The join condition is separated from other search conditions.
3. The ON clause makes code easy to understand.

Mithun Ashok said…
Hi Mona,

1. select ename, sal, trunc(10*sal/100), hiredate,to_char(hiredate,'YY') from emp where trunc(10*sal/100) = to_char(hiredate,'YY');

2. select ename, hiredate from emp where hiredate > (select hiredate from emp where ename='KING')
and hiredate < (select hiredate from emp where ename='SMITH');

This will not return any rows as there are no employees in this category, if you say any employee junior to KING and senior to SMITH then you will see some rows. Query for this is as below,

select ename, hiredate from emp where hiredate < (select hiredate from emp where ename='KING')
and hiredate > (select hiredate from emp where ename='SMITH');

Monalisa Singh said…
Hello sir,

Thank u so much sir, i easily understood those queries but m stil confused wid this 'ON' clause.
So can u plz help me out sir.

Anonymous said…
Can I follow the same procedure to install 11g in Windows 7, as the video shown for 10g installation?Is there any other method to uninstall 11g?
Mithun Ashok said…
Hi Mona,

ON in Join is ANSI syntax, using this syntax you can do both equijoin as well as non equijoin's.

Here you will join 2 tables like,

select * from emp e join dept d
on (here you will mention the condition using which the tables are joined like e.deptno = d.deptno).

Hope this helps.

Mithun Ashok said…
Hi Anonymous,

You can follow the same process to install 11g it is similar to 10g install.

To uninstall, refer to my videos on uninstalling oracle database.

akash kumar said…
This is Akash Kumar(Scientist) Sir Can you send
me the Questions Generally asked in interviews (Along with Questions You
asked in the class about basic select,functions,joins,
subquery etc..)
Unknown said…
I m so much happy learning SQL within this short period and with such easiest much thankful Mr.Mithun Ashok..but facing little difficult on joins ...
Anonymous said…
hi sir, can u post the ppt on co-related subqueries,
Unknown said…
sir,in my system i am getting only 4 tables how can i get more tables that u showed in the class can u please tell me sir .....
Unknown said…
Sir,when I give like the statament
Select* from emp where rownum =10;
Its show error
But when we gve the statment like
Select * from emp where rownum <=3;
Then it gve some result... why sir
Unknown said…
Email id
Unknown said…
hi sir its me mithun. one of your student.

actually I got job on business intelligence. In this they are teaching like dbms, etl, datawarehouse, reporting, business intelligence and congous it good to work on this..did i have good future in this.

waiting for your reply

thank you
Unknown said…
This comment has been removed by the author.

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1. SQL> SELECT empno, ename FROM emp WHERE Length(ename) = 4;

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