0:00	foreign
0:06	languages
0:11	before understanding what is a
0:13	relational query language let's see an
0:16	analogy let's say I wanted to have some
0:19	coffee so I am assigning the task of
0:21	preparing a cup of coffee to two people
0:23	let's say X and Y and let's assume I am
0:27	providing all the required resources
0:29	that are required for preparing the cup
0:31	of coffee and we know two people they
0:34	are X and Y to X I am just telling him
0:37	to prepare coffee but to the person why
0:40	I am informing each and every step on
0:43	how to prepare the coffee at the end we
0:45
know both X and Y will be preparing the
0:47
cup of coffee but the difference is 2x I
0:51
just said what is required but why I
0:54
instructed what is required and how to
0:57
get that with this analogy let's step
0:59
into the topic of the day the relational
1:02
query language and I will explain you
1:04
shortly how this analogy is related to
1:07
the topic so let's now see the
1:10
relational query languages at first we
1:12
must understand what is a query language
1:14
a query language is a language in which
1:18
a user requests for information from the
1:20
database we know database only is going
1:22
to store all our data whenever we want
1:24
some information or data from the
1:26
database what language is used for
1:28
requesting the data from the database
1:30
it's the query language
1:33
so a query language is a language in
1:36
which a user requests information from
1:38
the database and generally this query
1:40
language is considered to be at the
1:42
higher level than that of a standard
1:44
programming language why it is
1:46
considered to be at the higher level
1:47
let's say we are going to withdraw some
1:49
money from ATM in that case we will be
1:52
obviously going and visiting the ATM
1:54
machine there there will be an user
1:56
interface where we are going to interact
1:58
with the system through that user
2:00
interface only and that user interface
2:02
will be obviously written in high level
2:04
programming language but the thing is
2:06
all our data are stored in the back end
2:08
which is the database but from where we
2:10
are going to retrieve the data from the
2:12
front end which is written in the
2:14
programming language in that programming
2:16
language code only we are going to write
2:18
the query language code so already the
2:21
programming language is a higher level
2:22
language inside that we are going to
2:24
write the query language which is even
2:26
higher level than the standard
2:27
programming language say for example if
2:29
I want to retrieve my account balance
2:31
then the query related to that retrieval
2:34
of account balance will be embedded in
2:35
the programming language only and that's
2:37
why this point says that this query
2:39
language is actually in the higher level
2:41
than that of a standard programming
2:43
language and basically there are two
2:45
categories of query language the first
2:48
one is the procedural query language and
2:50
the second one is non-procedural query
2:52
language let's first see the procedural
2:55
query language in a procedural query
2:57
language a sequence of operations are
3:00
going to be executed on the database and
3:03
these sequence of operations are just to
3:05
compute the desired result in simple
3:07
terms we are going to write a query
3:09
where this query is going to carry out a
3:12
sequence of operations on the database
3:14
in order to get the result the desired
3:17
result and this is the job of a query
3:19
language obviously because we are going
3:21
to request for the information from the
3:22
database so we are going to supply some
3:24
queries then what is different with
3:26
procedural query language from
3:27
non-procedural query language anyway
3:29
both are query languages we are going to
3:31
write queries and databases is obviously
3:34
going to respond to the queries to be
3:35
precise in the form of tables now what
3:38
makes the difference between procedural
3:39
and non-procedural query language in a
3:42
procedural query language we are going
3:43
to write the query in such a way that we
3:46
are going to mention what data is
3:48
required from the database and we are
3:50
also going to mention how to retrieve
3:52
those data in a procedural query
3:54
language we are going to write a query
3:56
that query is going to contain the
3:58
information like what data is actually
4:01
required and how to retrieve those data
4:03
so this is about procedural query
4:05
language I hope now you can correlate
4:08
this with the analogy we saw two people
4:10
X and Y to x what we instructed what is
4:14
required so why what we instructed what
4:17
is required and how to get it in other
4:19
words 2x we just instructed to prepare
4:22
coffee but to why we instructed we need
4:25
coffee also we instructed why how to
4:28
prepare coffee this procedural query
4:30
language is like y in the analogy
4:33
because we are saying what is required
4:35
and also we are instructing how to
4:37
retrieve those data
4:39
so this is about the procedural query
4:41
language before we step into
4:43
non-procedural query language let's see
4:45
an example here the example for
4:47
procedural query language is relational
4:49
algebra in this chapter we are going to
4:51
focus on relational algebra at the time
4:53
I will explain you what is relational
4:55
algebra and why it is referred as a
4:57
procedural query language
4:59
we are done with the first category of
5:02
relational query language the procedural
5:04
query language let's now move on to the
5:06
second category the non-procedural query
5:09
language in non-procedural query
5:11
language the user describes only the
5:13
desired information it means we are
5:16
going to Simply say what data is
5:18
required are we going to instruct how we
5:20
are going to retrieve the data no need
5:22
to describe how to retrieve those data
5:24
if we instruct how to retrieve those
5:26
data it is procedural but what we are
5:29
talking about its non-procedural query
5:31
language where we are going to Simply
5:33
say what data is required and we are not
5:36
going to mention how to retrieve those
5:38
data and this language is like the X in
5:41
the analogy where to the X we just
5:43
mentioned we need coffee that's it so
5:46
non-procedural query language is like X
5:48
in the analogy and the example for
5:51
non-procedural query languages the
5:53
relational calculus we have two types
5:55
here the Tuple relational calculus and
5:58
the domain relational calculation so in
6:00
relational calculus we are going to just
6:02
say what data is required and we are not
6:04
going to explicitly say how to retrieve
6:06
those data so far we are done with the
6:09
procedural query language and the
6:10
non-procedural query language which are
6:13
coming under relational query language
6:15
before we sign out let's see few more
6:17
points about the relational query
6:18
language already we have understood what
6:20
is a query language and we also have
6:22
understood why it is at the higher level
6:24
than that of a standard programming
6:26
language and we know there are two
6:28
categories procedural and non-procedural
6:31
when we talk about this relational query
6:33
language basically this relational query
6:35
language is thirst and formal why it is
6:39
stars because the syntax of relational
6:41
query language is in the short version
6:43
but also not in a friendly way and
6:46
that's why I'm referring it as thirds so
6:48
relational query language statements are
6:50
ters and they are formal
6:52
and coming to the next point this
6:55
relational query language lacks the
6:57
syntactic sugar of the commercial
6:59
languages it means the syntax of this
7:01
language is not easier to read or
7:04
Express
7:05
if that is the case then why do we need
7:07
relational query languages because this
7:09
is going to be doing the fundamental
7:11
techniques of extracting the data from
7:14
the database and this is true because
7:16
the main intention of having query
7:18
language is to get the information from
7:20
the database in order to get the
7:22
information from the database we are
7:23
going for relational query languages
7:25
because they have the fundamental
7:27
techniques for extracting the data from
7:29
the database
7:31
and that's it guys I hope you guys
7:33	enjoyed this presentation and thank you
7:35	for watching
7:36	[Applause]
7:38	[Music]