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Created page with "'''Title of the Script: NULL Values and UPDATE Statement'''. '''Author: Ketki Bhamble''' '''Keywords: '''PostgreSQL, pgAdmin 4, Logical operators, AND, OR, NOT, WHERE, EduPy..."

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'''Title of the Script: NULL Values and UPDATE Statement'''.

'''Author: Ketki Bhamble'''

'''Keywords: '''PostgreSQL, pgAdmin 4, Logical operators, AND, OR, NOT, WHERE, EduPyramids, video tutorial.

{|border=1
|-
|| '''Visual Cue'''
|| '''Narration'''
|-
|| '''Slide 1'''

'''Title Slide'''
|| Welcome to this Spoken Tutorial on''' NULL Values and UPDATE Statement'''.
|-
|| '''Slide 2'''

'''Learning Objectives '''
|| In this tutorial, we will learn how to,
* Insert and Display '''Null''' values and
* '''UPDATE''' Statement
|-
|| '''Slide 3'''

'''System Requirements '''
* '''Ubuntu 24.04''' '''LTS'''
* '''PostgreSQL version 18.1''', and
* '''PgAdmin 4 version 9.11'''.
|| To record this tutorial, I am using the following setup.
|-
|| '''Slide 4'''

'''Pre-requisites '''

[https://edupyramids.org https://EduPyramids.org] '''

|| To follow this tutorial,
* Learners should have '''PostgreSQL''' and '''p g Admin 4.'''
* For the prerequisite '''PostgreSQL''' tutorials, please visit this website.
|-
|| '''Slide 5'''

'''Code Files '''

The following code file is required to practice this tutorial:
* '''nvu-commands.txt'''

This file is provided in the Code Files link on this tutorial page.
|| The following code file is required to practice this tutorial.

This file is provided in the '''Code''' '''Files''' link of this tutorial page.

Please download and extract the file.
|-
||
|| Let us get started.
|-
|| '''Slide 6'''

'''What is a NULL Value?'''
|| A '''null''' value is an unknown or missing value.

If a field has no value it can be left blank as no data stored in it.
|-
|| '''Slide 7'''

'''Syntax of Null value'''

'''SELECT column_names'''

'''FROM table_name'''

'''WHERE column_name IS NULL<nowiki>; </nowiki>'''
|| This is the syntax to show a '''Null''' value.

'''IS NULL''' clause checks for fields that have no stored values.
|-
||
|| I have opened the '''p g Admin 4 '''interface and connected to the localhost server.
|-
|| Type:''' INSERT INTO students (studentid, studentname, city, gender, dob, cgpa)'''

'''VALUES ('S116', 'Ravi', 'Pune', 'M', NULL, NULL);'''

Click the''' Execute query icon.'''
|| Let us insert a '''NULL''' value.For this, type the following query.

Here the '''NULL''' keyword is used to insert null values.

Let us execute the query.

The query is returned successfully.
|-
|| Type: '''INSERT INTO students (studentid, studentname, city, gender)'''

'''VALUES ('S117', 'Kiran', 'Pune', 'M');'''

Click on the''' Execute query button'''.

ADD ANNOTATION.( '''CGPA''' and '''DOB''' are automatically set to '''NULL''')
|| Type the following query and execute it. Here, '''C G P A''' and '''D O B columns''' are automatically set to '''NULL'''.
|-
||
|| We can add a '''NULL value''' by inserting a record without specifying its value.
|-
|| Type: '''SELECT * FROM students'''

'''WHERE cgpa IS NULL;'''
|| Type the following query.

Here we are using the I'''S NULL '''clause.

Let us execute the query.

The output displays details of students whose '''C G P A''' is currently not recorded.
|-
||
|| Here, the '''D O B''' and '''C G P A''' values are not known.
|-
||
|| Now let us see another example.
|-
|| Type: '''SELECT studentid, studentname'''

'''FROM students'''

'''WHERE cgpa IS NULL;'''

Click on the''' Execute query button'''.
|| Type the following query and execute it. This query displays studentid and their names whose '''C G P A''' value is '''NULL'''.
|-
||
|| Let us update the record so that it no longer displays NULL.
|-
|| '''Slide 8'''

'''UPDATE Statement'''
|| '''UPDATE''' Statement is used to modify existing records in a table.
|-
|| '''Slide 9'''

'''Syntax of UPDATE Statement'''.

'''UPDATE table_name'''

'''SET column1 = value1, column2 = value2, ...'''

'''WHERE condition; '''
|| Here is the syntax of the UPDATE statement.'''UPDATE''' specifies the table to be modified.

'''SET''' assigns new values to one or more columns.

'''WHERE''' selects the records that need to be updated.
|-
|| Type: '''UPDATE students'''

'''SET cgpa = 8.1'''

'''WHERE studentid = 'S116';'''

Click on the''' Execute query button'''.
|| Let us update the Null value.

Type this query.

Here the '''SET''' keyword sets the C G P A value to 8 point 1.

Let us execute the query.
|-
|| '''Cursor on Query returned successfully in 322 msec.'''
|| The output shows that the query is updated.
|-
|| Type:

'''SELECT * FROM students '''

'''WHERE studentid = ‘S116’;'''
|| Now let us type this query and execute it.

We can see that a new record is added to the table.
|-
|| Show the table and point to M in the records.
|| Let us update the records of students with studentids S116 and S117
|-
|| Type the following:'''UPDATE students'''

'''SET gender = 'Male''''

'''WHERE studentid = 'S116''''

'''OR studentid = 'S117';'''

Click on the Execute Query button.
|| Type the following query.

In this query we will set the gender to male.

Let us execute the query.

The table is now updated.
|-
|| Type: '''SELECT * FROM students; '''

Click on the Execute Query button.

Point to the gender columns of the students.
|| Let us display the entire table.Type this query and execute it.

We can see that in the gender column M is updated to Male for studentids '''S116 '''and''' S117'''.
|-
|| '''Slide 10'''

'''Summary'''

In this tutorial, we have learnt how to,
* Insert and Display Null values and
* UPDATE Statement
|| With this, we come to the end of this tutorial.

Let us summarise.
|-
|| '''Slide 11'''

'''Assignment'''

'''As an Assignment, '''

Insert a student record with a NULL CGPA value.

Update the NULL CGPA value for one student.

Verify the updated record using a SELECT query.
|| We encourage you to do this assignment.
|-
|| '''Slide 12'''

'''Thank you'''

This '''Spoken''' '''Tutorial''' is brought to you by '''EduPyramids''' Educational Services Private Limited SINE IIT Bombay.
|| Thank you for joining.
|-
|}

PostgreSQL-Database/C2/NULL-Values-and-UPDATE-Statement/English - Revision history

Ketkinaina: Created page with "'''Title of the Script: NULL Values and UPDATE Statement'''. '''Author: Ketki Bhamble''' '''Keywords: '''PostgreSQL, pgAdmin 4, Logical operators, AND, OR, NOT, WHERE, EduPy..."