Lecture10.txt

Lecture-10:
IS NULL & IS NOT NULL in SQL || Handle Null Values in Database:

Null Values: A field with NULL values has no value. Null value is different from zero (0) and white-space (“_”)
In SQL NOT Null Values= 0, “ “ (space)
                      Null Values= Blank/Empty
Example: Amazon => Database => Customer
                Sl. No.            Name                     Address                         Age
                   1.              Rupu                     Agarpara                         22
                   2.              Rup                         __                             0
                   3.              Rupayan                    Fulia                           24
                   4.               __                       Newtown                          20
[Note: In SQL, we can’t compare the null values with operators. Because null values do not exist, so we can’t compare null values with operator.]
Syntax: select *(or use “column_name”) from table_name where column_name Is Null;
[Note: Is Null is used to find null values.]
Command: select * from Customer where Name Is Null;
Output: 
                Sl. No.            Name                     Address                         Age
                   4.               __                      Newtown                          20

Is NOT Null: It is used to check that my table contains any value or not.
Syntax: select *(or use “column_name”) from table_name where column_name Is NOT Null:
Command: select * from Customer where Address IS NOT Null;
Output:
                Sl. No.            Name                     Address                         Age
                   1.              Rupu                     Agarpara                         22
                   3.              Rupayan                    Fulia                           24
                   4.               __                       Newtown                          20

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