SQL JOINS

Swapnali Pawar GCEKarad
Database Lab
Swapnali Pawar
JOINS in SQL
1

 Oracle JOINS are used to retrieve data from multiple tables.
 JOIN clause combines rows from two or more tables.
 creates a set of rows in a temporary table
Joins
2

Types of SQL JOIN
❖ EQUI JOIN
● EQUI JOIN is a simple SQL join.
● Uses the equal sign(=) as the comparison operator for
the condition
● NON EQUI JOIN uses comparison operator other than
the equal sign.
● The operators uses like >, <, >=, <= with the
condition.
❖ NON EQUI JOIN
3

Types of SQL EQUI JOIN
❖ INNER JOIN
❖ OUTER JOIN
● Returns only matched rows from the
participating tables.
● Match happened only at the key record of
participating tables.
● Returns all rows from one table and
● Matching rows from the secondary table and
● Comparison columns should be equal in both
the tables.
4

List of SQL JOINS
• INNER JOIN
• LEFT JOIN OR LEFT OUTER JOIN
• RIGHT JOIN OR RIGHT OUTER JOIN
• FULL OUTER JOIN
• NATURAL JOIN
• CROSS JOIN
• SELF JOIN
5

• SQL EQUI JOIN performs a JOIN against equality or
matching columns values of the associated tables. An
equal sign (=) is used as comparison operator in the
where clause to refer equality.
• You may also perform EQUI JOIN by using JOIN keyword
followed by ON keyword and then specifying names of the
columns along with their associated tables to check equality
• Syntax :
SELECT column_list FROM table1, table2....
WHERE table1.column_name = table2.column_name;
• Example –
SELECT student.name, student.id, record.class, record.city
FROM student, record WHERE student.city = record.city;
1. EQUI JOIN
6

1. EQUI JOIN 2nd way
Syntax :
SELECT column_list FROM table1 JOIN
table2 ON (join_condition)
Example –
SELECT student.name, student.id,
record.class, record.city FROM student
JOIN record ON student.city =
record.city;
7

Select * from Record;
Select * from Student; SELECT student.name, student.id, record.class,
record.city
FROM Student
JOIN Record
ON Student.city = Record.city;
Equi Join Example
9

NON-EQUI JOIN
• Non-equi joins are joins whose join conditions use
conditional operators other than equals
• The SQL NON EQUI JOIN uses comparison operator
instead of the equal sign like >, <, >=, <= along with
conditions.
• Syntax:
SELECT * FROM table_name1, table_name2
WHERE
table_name1.column [> | < | >= | <= ]
table_name2.column
10

• A self join is a join in which a table is joined with itself
(Unary relationships), specially when the table has a
FOREIGN KEY which references its own PRIMARY KEY.
• To join a table itself means that each row of the table is
combined with itself and with every other row of the
table.
• The self join can be viewed as a join of two copies of the
same table.
self join
12

table_A
SELECT *
FROM table_A X, table_A Y
WHERE X.A=Y.A;
Output
table_A
13

INNER JOIN (simple join)
• It is the most common type of join. Oracle INNER JOINS return all rows
from multiple tables where the join condition is met.
• Syntax
SELECT columns FROM table1 INNER JOIN table2 ON table1.column =
table2.column;
14

LEFT OUTER JOIN
• Another type of join is called an Oracle LEFT OUTER JOIN. This type of join
returns all rows from the LEFT-hand table specified in the ON condition
and only those rows from the other table where the joined fields are equal (join
condition is met).
• Syntax
SELECT columns FROM table1 LEFT [OUTER] JOIN table2 ON
table1.column = table2.column;
• In some databases, the LEFT OUTER JOIN keywords are replaced with LEFT
JOIN.
• The Oracle LEFT OUTER JOIN would return the all records from table1 and
only those records from table2 that intersect with table1.
15

RIGHT OUTER JOIN
• Another type of join is called an Oracle RIGHT OUTER JOIN. This type of join
returns all rows from the RIGHT-hand table specified in the ON condition
and only those rows from the other table where the joined fields are equal (join
condition is met).
• Syntax
SELECT columns FROM table1 RIGHT [OUTER] JOIN table2 ON
• In some databases, the RIGHT OUTER JOIN keywords are replaced with
RIGHT JOIN.
• The Oracle RIGHT OUTER JOIN would return the all records from table2 and
only those records from table1 that intersect with table2.
16

FULL OUTER JOIN
• Another type of join is called an Oracle FULL OUTER
JOIN. This type of join returns all rows from the LEFT-
hand table and RIGHT-hand table with nulls in place
where the join condition is not met.
• Syntax
SELECT columns FROM table1 FULL [OUTER] JOIN table2 ON
• In some databases, the FULL OUTER JOIN keywords are replaced
with FULL JOIN.
• The Oracle FULL OUTER JOIN would return the all records from
both table1 and table2.
17

ROLL_NO NAME ADDRESS
1 Swapnali karad
2 Rugveda Pune
3 Sarika Mumbai
4 Chaitrali kolhapur
5 Pratima karad
6 Rupali pune
COURSE
_ID
COURSE_NAME ROLL_NO
101 CSE 1
101 CSE 2
102 MCA 3
103 BCA 4
105 IT 5
106 ENTC 6
StudentTable CourseTable
Primary Key
Foreign Key
Join Operation requires at least 1 Common Attribute
18

1. Primary Key-
Create table student(Roll_no int primary key,
name varchar(20),
Address varchar(20));
2. Foreign Key-
Create table Course(course_id varchar(10),
course_name varchar(30)
Roll_no int references student(Roll_no));
3. Insert into student values(1,'Swapnali','karad');
4. Insert into Course values(101,'CSE',1);
1.CreateTables with primary key & Foreign Key
& insert Records in that
19

EQUI-JOIN-
Select student.roll_no,Name,Course_name from
student , course where
student.roll_no=course.roll_no;
select student.roll_no,Name,Course_name
from student JOIN course On
20

NON-EQUI JOIN-
Select student.roll_no,Name,Course_name from student,course
where student.roll_no!=course.roll_no;
21

SELF JOIN
Select s1.roll_no,S1.name,S2.Address from Student S1,student
S2 where S1.Address=S2.Address and S1.Roll_no!=S2.roll_no;
22

INNER JOIN
select student.roll_no,name,course_id,course_name from
student Inner Join Course on
23

LEFT OUTER JOIN
Select student.roll_no,name,course_id,course_name from
student Left Outer Join Course on student.roll_no=course.roll_no;
24

RIGHT OUTER JOIN-
Select student.roll_no,name,course_id,course_name from student
RIGHT OUTER JOIN Course on student.roll_no=course.roll_no;
25

FULL OUTER JOIN-
Select student.roll_no,name,course_id,course_name from student
FULL OUTER JOIN Course on student.roll_no=course.roll_no;
26

Student Activity
1.CreateTable Employee & Department using Primary key &
Foreign key Respectively.
ENO E_Name Address DeptNo Location ENO
Employee Department
2. Perform Equi Join,Non-Equi Join ,Self Join,Inner Join,Left Outer
Join,Right Outer Join,Full Outer Join on Employee & Deparment
Table.
3. Find Employee Name who worked in department having
Location same as Address
27

SQL JOINS

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