0:02
[Music]
0:12
hello friends welcome back to our
0:13
channel so in today's session we will
0:15
discuss about one more concept in dbms
0:18
that is a relationships
0:26
so first we will see what is this
0:28
relationships and why we required in the
0:30
dbms and then we will see the categories
0:33
of these relationships that means how
0:34
many uh types of relationships are there
0:37
right so first
0:39
why we require these relationships
0:41
so coming to the relational database
0:44
management system here the data will be
0:46
represented in terms of rows and columns
0:49
and we call them as a tables
0:52
tables so there will be a multiple
0:54
tables for a data so there will there
0:57
will be a table 1
0:58
there will be a table 2
1:01
there will be a table 3
1:04
etc right so the complete data will be
1:07
divided into at different tables now
1:10
after that we have to relate these two
1:12
tables these different tables right so
1:15
we have to relate
1:17
relate these tables right from one
1:19
record to another record so that
1:22
will be called as a
1:24
relationship
1:26
relationship so by using this
1:29
relationship one table data will be
1:32
related to the data available in the
1:34
another table and further for this
1:36
purpose we are going to use the two
1:38
different keys like
1:40
primary key
1:42
primary key
1:46
foreign key
1:47
so by using these two keys will relate
1:50
different tables so
1:52
what about i mean what exactly this
1:54
primary key what is meant by this
1:56
foreign key we'll see in the next
1:57
session so we'll see the different types
1:59
of keys in the next session so by using
2:01
these keys we will relate the different
2:04
tables
2:05
right so that we call it as a
2:07
relationship
2:08
relationship now we will see what are
2:11
the different types of relationships
2:13
available
2:14
in our dbms
2:18
the first one
2:22
one to one relationship
2:27
one too many relationship
2:34
many too many relationships
2:36
so there are three types of
2:38
relationships one to one
2:40
one too many sorry one too many and
2:43
one two sorry many too many so these are
2:45
the different types of relationships
2:47
so
2:48
let us take this one to one relationship
2:51
one to one relationship
2:53
so here we are having two different
2:55
tables
2:58
okay so first of all see
3:02
let us consider
3:06
table 1
3:11
and this one is a
3:15
table 2. so these are all the
3:18
records in the table in the table one
3:21
and in the table two
3:23
now
3:25
if
3:26
one record
3:28
one record here record means it tuple or
3:31
we can also call it as an entity right
3:34
or a row
3:36
so one record
3:38
of table one
3:40
of table one
3:42
is
3:43
related to
3:45
is related to
3:47
only one record
3:51
one record
3:52
of table two
3:56
table two
3:57
and
4:00
vice versa
4:02
vice versa that means if you consider
4:04
one record of table two that should be
4:06
related to only one record of table one
4:09
so such type of relationship we call it
4:12
as a
4:12
one to one relationship
4:15
one to one so if you consider one record
4:17
in table one that should be related to
4:20
exactly one record in the table two for
4:23
example consider
4:26
a
4:26
person a person details in table one
4:30
and in table two
4:32
let it be some passport details passport
4:34
details you can see one person will be
4:37
ha is related to only one passport
4:39
number so one for one person will be
4:41
having only one passport number right
4:44
similarly one passport will be given to
4:47
only one person so one password will be
4:49
given to not more than one right so
4:53
this type of relationship this type of
4:55
relationship we call it as a one-to-one
4:58
so a person so one person is associated
5:01
with only one passport
5:03
similarly one passport is given to only
5:07
one person so one passport will not be
5:09
given to multiple persons and one person
5:12
will not get a multiple passports so
5:14
such type of relationship we call it as
5:16
a one to one so one record in table one
5:19
is related to exactly one recording
5:22
table two similarly one recording table
5:24
two exactly related to
5:26
one recording table one this is called a
5:29
one two one relationship the next one
5:37
one too
5:38
many
5:40
one too many so in this one too many the
5:43
name itself indicates one record of
5:45
table one
5:46
one record of table one should relate to
5:49
multiple records of table two okay one
5:52
record of table one
5:54
should be related to multiple records of
5:57
table two similarly
5:59
one record of table two should exactly
6:01
match with only one
6:03
record of table one
6:05
right see don't get confused
6:09
one
6:10
record record or row or a tuple or
6:13
entity whatever it may be one record
6:15
of
6:16
table 1.
6:20
is
6:22
related to
6:27
multiple
6:30
records
6:31
of
6:35
table two that's the first point so one
6:37
record of table one is related to
6:40
multiple records of table two
6:42
and
6:46
one record
6:49
of
6:51
table two
6:55
is related to
6:58
only
6:59
one
7:02
record
7:03
of
7:04
table one that means the vice versa is
7:06
not possible the vice versa is not
7:08
possible see consider
7:16
are two tables here
7:25
there are two tables
7:44
they will do
7:45
so if this table one consists of
7:48
branch
7:49
okay bank consider the banking okay
7:52
banking sector
7:53
banking sector
7:55
so one branch
7:59
one branch
8:02
multiple accounts
8:06
multiple accounts so different
8:08
users why different users will be having
8:11
different accounts
8:12
so there will be different types of
8:14
accounts savings account current account
8:15
what etc etc joint accounts so
8:18
one branch manages
8:21
multiple accounts
8:24
one branch
8:26
manages multiple account that means one
8:29
record of table one is related to
8:32
multiple records of table two
8:35
okay one record of table one is related
8:38
to multiple records of table two
8:41
the vice versa is
8:43
not possible so
8:44
multiple accounts multiple accounts
8:47
will be
8:48
managed by a single branch
8:51
so
8:52
one record of table two should be
8:55
associated with only one record of table
8:58
one
8:59
so that's what we have written here so
9:00
one record of table one that means a
9:02
branch
9:03
is related to multiple records of table
9:05
two so one branch is managing different
9:08
accounts multiple accounts multiple
9:10
users
9:11
okay similarly one record of table two
9:13
that means one account of table two
9:16
is related to only one record of table
9:18
one so that will be managed by a single
9:20
branch it will not be managed by
9:22
multiple branches
9:24
right so this type of relationship we
9:26
call it as in one too
9:28
many
9:29
one two main so one record of table one
9:32
related to multiple records of table two
9:35
and one record of table two should be
9:37
related to only one record of table one
9:40
so the third category
9:42
many too many
9:43
so let us see
9:47
here the name itself indicates many too
9:49
many
9:54
see
10:02
many too many relationship many too many
10:04
means
10:07
one record of table one is related to
10:10
multiple records of table two and one
10:12
record of table two is related to
10:14
multiple records of table one
10:17
okay see
10:20
one record
10:22
one record
10:23
of table 1
10:26
of table 1
10:28
is related to
10:32
multiple records
10:38
of table two
10:41
and vice versa is also possible
10:44
so
10:45
one record
10:48
of table two
10:53
is related to
10:58
multiple records
11:01
multiple records
11:03
of
11:05
table one
11:06
right so this this type of relationship
11:09
we call it as a many-to-many
11:11
example
11:13
consider a table
11:17
consider a table
11:21
so s1
11:23
s2
11:24
s3
11:26
s4
11:27
so this is a table
11:30
one
11:32
and coming to the second table
11:34
right on the second table
11:40
c one c2 c3 c4
11:44
this is a
11:46
table 2 so this is a student table
11:52
this is a course table
11:54
course table so here you can observe
11:58
so student can enroll multiple courses
12:02
student can enroll multiple courses
12:06
similarly one course
12:08
can be uh
12:10
[Music]
12:11
i mean enrolled by multiple students
12:14
one co one course can be enrolled by
12:16
multiple students right see s1 and roles
12:20
c1 c2 c3 c4
12:24
similarly s2
12:26
and roll c1 c2
12:28
c3 c4
12:30
s3 c1 c2 c3 c4
12:34
s4 c1 c2 c3
12:38
c4
12:40
right so student 1 can enroll all the 4
12:43
courses similarly student 2 can enroll
12:45
all the 4 courses so c1 is enrolled by
12:49
the students s1 and s2
12:52
okay so for example if the s1 enrolls
12:54
the screw core says c1
12:57
c2 c3 c4
12:59
s2 enrolls the core says c1 c3 c4
13:04
s3 enrolls this courses three c3 and c4
13:08
s4 enrolls the course c1
13:10
now you can observe
13:12
one record of one table s1 is a one
13:15
record of one table is related to
13:18
multiple records of another table that
13:20
means a course table so multiple records
13:23
c1 is one record c2 is another record c3
13:25
is another record and c4 another record
13:27
so s1 is related to multiple records
13:30
right similarly if you observe the vice
13:33
versa so c1 is related to
13:37
s1
13:39
s2 es4
13:41
c2 cores 2 is enrolled by s1
13:46
and c3 is enrolled by s1
13:49
s2 es3
13:52
c4 is enrolled by
13:54
s1
13:55
s2
13:56
s3
13:57
so you can observe the vice versa also
14:00
one record c one is one recording table
14:02
two one record is associated or related
14:05
with multiple records of table one s one
14:08
is one record s two is another s4 is
14:10
another
14:12
right so this type of relationship this
14:15
type of relationship we call it as a
14:17
many too many
14:19
this type of relationship we call it as
14:21
a mini to many relationship
14:25
okay so
14:26
one record of table one is related to
14:29
multiple records of table two similarly
14:32
one record of my table two related to
14:35
multiple records of table one
14:38
so these are the three categories of
14:41
relationships three types of
14:42
relationships one to one one to many and
14:45
many too many
14:47
right so hope you understood these
14:49
different types of relationships in dbms
14:51
so hope you understood and if you are
14:53
having any doubts regarding this one
14:54
feel free to post your doubts in the
14:56
comment section definitely i will try to
14:57
clarify all your doubts if you really
14:59
enjoyed my session like my session share
15:02
my session with your friends and don't
15:03
forget to subscribe to our channel
15:05
thanks for watching thank you very much