Database object, sub query, Join Commands & Lab Assignment

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Chapter DiscussionAbout Database Object, SubQuery, Joining ( 3 chapters inone class)
Database has few objects. They are
1. Table : Basic unit of storage which represented as rows and columns format.
2. View : It is logical subsets of data from more than one table.
3. Sequence : It is used to generate Unique integer number.
4. Synonym : It is an ulternate name for other database objects.
5. Index : Oracle server used index to faster access the rows using pointer.
View : It is logical subsets of data from more than one table. There are two types of view.
1. Simple view
2. Complex View
Why we use view
1. To restrict Data access : View doesnot allows to access all columns from table. It is created selected
columns only. Importants columns hides from other user.
2. Make complex query easy : You don’t need everytime specify join command. Only write once complex
commnd and make view. Then only access that view.
Simple View
The view which consists of only one tble is called simple view. The DML operation can perform with
this view. If you want restrict DML operation you can write WITH READ ONLY statement to avoid DML
operation
Complex View
The view which consists of more than one table is called Complex View. It restricts DML operation.
ROLL NAME DOB MARK
1 A 12-JAN-1990 500
2 B 16-JUN-1992 408
3 C 19-JUL-2000 557
4 D 30-MAY-1997 300
5 E 22-SEP-2000 490
Create View v1 as select roll,mark from student;
Above command create view name v1 consists of two column;
You can define your own column inside view
Create or replace view v1(MyRoll,MyMark) as select roll,mark from student;

Above command updated your view (because i write replace command) with MyRoll and MyMark column.
If you write select statement
Select * from v1;
It display like
MyRoll MyMark
1 500
2 408
3 557
4 300
5 490
You can update view
Update set mark=900 where roll=1;
After select from v1
MyRoll MyMark
1 900
2 408
3 557
4 300
5 490
Same also updated in Table
Select * from student;
ROLL NAME DOB MARK
1 A 12-JAN-1990 900
2 B 16-JUN-1992 408
3 C 19-JUL-2000 557
4 D 30-MAY-1997 300
5 E 22-SEP-2000 490
If you want to restrict DML operation in view then use WITH READ ONLY
E.g.
Create View v2 as select roll,mark from student where roll=2 WITH READ ONLY;
Then when you try to update view v2 whose roll is two it display arror.

Complex view
The view which consists of more than one table is called Complex table. Here DML command is
restriction
See the E.g
Create view v3(MyRoll,MyName,MyDept,Price) as Select stud1.roll,stud1.name,dept.name,dept.price from
stud,dept where stud.roll=dept.roll;
Here you can see view v3 is (MyRoll,MyName,MyDept,Price) is created. It is consists of 4 columns.
Sequence
Sequence is used to create to generate unique integer values. Declaraton of Synnym
Create sequence sequence_name : sequence name
Increment by n - sequence increment by n, specify the interval between sequence number
Strart with n – n is specified by the starting value of sequence
Max value n – n specified where sequence number will be start.
Min value n - n specify the minimum sequence no
Cycle / nocycle – after reach at max valueit will be recycled. Means again starts value from minimum no.
Cache n/ nocace – how many number oracle can allocate memory to store in memory. Numbers are faster
access from memory.
See how created ?
Create sequence s1 //sequence name is s1
Increment by 1 //sequence is incremented by 1
Start with 3 //sequence start value
MaxValue 30 //sequence will stop as it reached 30
MinValue 2 //After reached 30 next time it start from 2. Not again from start value. And minvalue
//should less than start value.
Cycle //cycle means value will be recycled after reach max value.
Error:ORA-04013 Number to Cache must be less than one cycle. So max value should specify 22 or above.
Default cache is 21.
Sequence Created.
To check sequence
Select s1.nextval from dual;
Select s1.currvalue from dual;
To verify user sequence from user_sequence data dictionary
SELECT sequence_name, min_value, max_value, increment_by, last_number FROM user_sequences;

You can also write
Insert into stud values(s1.nextval,’aa’,789);
To drop sequence
Drop sequence sequence_name;
Drop sequence s1;
Synonym
It is called alternate name for table.
E.g.
Create synonym sn for student_sce_dept;
Then instead of write big table name we use it through small name sn.
E.g. select * from sn; it display data from student_sce_dept.
To drop synonym
Drop synonym sn;
Index
Is used by the Oracle server to speed up the retrieval of rows by using a pointer
two types index
Automatically: when we declare primary key or unique key.
Manually: Users can create nonunique indexes on columns to speed up access to the rows.
CREATE INDEX emp_last_name_idx ON employees(last_name);
Index created.
SUB QUERY
It is called inner query. The query which is exists in another query is called inner query. It is also called nested
query.
Features
1. It is enclosed with parenthesis
2. It is written right side of outer query.
3. Inner query first executed then outer query executed.

4. Outer Query executed after result return from inner query.
Two types of inner query
Sometimes inner query returns two types result. First single result second multiple row result. Based upon this
It is two types.
1. Single row return inner query
2. Multi row return inner query
E.g.
Select name from student where mark<(select mark from student where name=’Ramesh’);
Right side is called inner query. First we should know what is mark of Ramesh. Then we select mark those are
below ramesh mark. In bold and underlined mark is called inner query.
Single row returns inner query operator
1. =
2. >
3. <
4. >=
5. <=
6. <>
Multiple rows returns inner queries
1. IN : If outer query matched any value from IN operator then it returns result.
2. ANY : <ANY means Less than the maximum. >ANY means more than the minimum.=ANY is equivalent
to IN
3. ALL : <ALL means less than the minimum and >ALL means more than the maximum.
Select name from student where mark in (300,700,800);
Or
Select name from student where mark in(select mark from student where mark<900);
JOIN command
Join command is used to return query more than one table.
Prior to Join Oracle8i or Prior
1. Cartesian Join
2. Equi-Join same as simple join same as inner join
3. Non-Equi Join
4. Outer Join
5. Self Join

Oracle 9i or Next
1. Cross Join
2. Natural Join
3. Using clause
4. ON clause
5. Full or two sided outer join
CartesianJoin
When we specify join command invalid or ommit then result of cartesian join will be produced
between two table.
E.g.
Selet roll,name,mark,branch from stud,dept;
Here stud has 5 rows and dept has 4 rows. Then total 5*4=20 rows will be ceated.
Equi Join:
It is based upon equality of two values of same column of two different tables. It use the (=) operator.
Select stud.roll,name,mark,branch from stud,dept where stud.roll=dept.roll;
It display roll,name from stud table mark branch from dept table those roll are same to both table. (=)
Table alias
Select s.roll,s.name ,d.mark,d.branch from stud s,dept d where s.roll=d.roll;
Above we specify alias name for both table s & d. S is alternate name for stud table and D is alternate
name for Dept table. Advantages No need to write tablename repeatedly. Only use the shortcut name.
For faster write the query.
Ambiguity inColumn.
Here roll is common column for stud and dept table. When we write query
select roll,name,mark,branch from stud,dept .............
Oracle server will be confuse to take about roll. Because it is common. So we specify which table roll
column we want to display. Modified query is
Select stud.roll , name, mark branch from stud,dept where stud.roll=dept.roll;

Non Equi Join
The operator which are used other than (=) is called Non Equi Join. Operators are used
1. >
2. <
3. <>
4. Between
Select s.name,d.mark from stud s,dept d where s.mark between d.high_mark and g.low_mark;
Left outer Join / Right Outer Join / Full Outer Join
Outer Join-It is an extension of inner join. It returns rows that are matched to both tables. And also returns
those are not matched to another table.
It returns the rows those are missed in join condition. Outer join symbol is (+) sign
e.roll(+)=d.roll //left outer join It returns the rows that are matched to both table except return rows those
that are not matched to the first table.
e.roll=d.roll(+) //right outer join it returns the rows that are matched to both table except returns the rows
that are not matched to the second table.
Full outer join: The join between two tables, that returns the result of an inner join as well as the result of left
outer join and return result of right join is a full outer join.
Full outer join
select name,mark from join7,join8 where join7.roll(+)=join8.roll union all select name,mark from join7,join8
where join7.roll=join8.roll(+)
Right Outer Join
select name,mark from join7,join8 where join7.roll=join8.roll(+);
Left Outer Join
select name,mark from join7,join8 where join7.roll(+)=join8.roll;

Self Join
From Stud d Natural Join Dept d; automatically choose same column name by oracle.
From stud s join dept d using (roll) // using clause is used to specify column name by user choice in join
condition
From stud s join dept d on(s.roll=d.my_roll) on clause is used to specify that have different column name.
Here roll & my_roll is not matched
Left outer join
select s.name,d.mark from join7 s left outer join join8 d on (s.roll=d.roll)
Right outer join
select s.name,d.mark from join7 s right outer join join8 d on (s.roll=d.roll)
Full outer join
select s.name,d.mark from join7 s full outer join join8 d on (s.roll=d.roll)
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ASSIGNMENT ON DATABASE OBJECT,SUB-QUERY AND JOIN COMMAND
STUDENT
STU_ROLL NAME DOB MARK BRANCH SECTION
AMIT 13/05/2010 600 SCE IT-1
AJAY 25/09/2009 550 IT IT-2
ROHIT 15/12/2008 450 IT CS-1
MUKESH 02/11/2007 390 SCE CS-2
JOHN 30/03/2005 400 IT CS-3
FACULTY
FACULTY_ID FAC_NAME STU_ROLL FAC_SUBJECT CLASS_ROOM CLASS_DATE_TIME
JOSEPH JAVA C1
STEPHEN C++ C2
RICHARDSON DOTNET C3
JAMES PHP C4
AKS ORACLE C5
TIPS:- CLASS_DATE_TIME DATATYPE IS TIMESTAMP(2) - TIMESTAMP IS USED FOR TO SPECIFY TIME. 2
MEANS AFTER SECOND VALUE FRACTION VALUE WON’T DISPLAY. ONLY TWO DIGIT SECOND DISPLAY.
INSERT INTO TABLE VALUES(TO_DATE(’12-JAN-2001 13:34:56’,’DD-MON-YY HH24:MI:SS’));
1. Enter exact data into student table. But roll should insert using sequence, it should start from 1 and
increment by 1.[total 5 records]
2. Enter exact data into faculty table. But faculty id should insert using sequence, it should start from 1
and increment by 3[total 5 records]. E.g. 1, 4, 7, 10, 13 Also enter exact student roll into faculty table
from referencing student table by using sequence but it should be increment by 2. E.g. 1, 3, 5, 7, 9
[total 5 records]
3. Waq to display sequence name, minimum value, maximum value from all created sequences.
4. Waq to drop these two sequences.
5. Create synonym s55 for student table. And query all rows from synonym. Then drop it.
6. Create view stv1 from student table by selecting roll, name , mark & branch column.
7. Waq to update marks from all rows from stv1 view.
8. Waq to create view stv2 from student table selecting roll, name, dob & mark of rollno 3 which can’t be
deleted from view.
9. Drop these two view from database.
10. Waq to create view st_fa from student & faculty selecting stu_roll, stu name, faculty id, faculty name
where rollno of student table should same to student roll of faculty table.
11. Select and drop st_fa view.
12. Waq to display the student roll, name, dob, mark and faculty name, subject, classroom, from student,
faculty table those student rollno are common to student rollno of faculty table using equi join.

13. Waq to display the all distinct rollno of student table those student rollnos are less than from faculty
table rollno using non equi join.
14. Waq to join student & faculty table without using any join command. And check how many rows
created.
15. Waq to check from faculty table, which student’s rollno and faculty’s id are same. Then display their
faculty names only.
16. Waq to display student roll,name & facult id, fac name from student and faculty tables those are
common roll no by using natural join.
17. Waq to display student’s roll,name and faculty id, fac name from student,faculty table by using ‘using’
clause.
18. Waq to display student roll,name & faculty id, fac name from student, faculty where faculty id and
student roll are same.
19. Waq to display student roll, name, mark, fac id, fac name from student, faculty table those are
common rollno to both table except those rollno of student table are also not matched to faculty
table.
20. Waq to display student roll, name, mark, faculty id, fac name from student,faculty table those are
common rollno except display fac id, fac name of corresponding rows of stu rollno of faculty table
those are not matched to student table rollno.
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