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Anonymous User

Anonymous User

17-Sep-2018

The different types of NULL values in Database like -

Blank value.
Empty value.
Zero value.
Optional value.
Invalid value.
void value.
Nothing value.
Missing value.
The lowest value.
Ignorable value.

1). Handle NULL value by procedure

 declare @value int=null;
if @value is NULL
begin
  Select 'Value is NULL' AS Result
end
set @value=1
if @value is NOT NULL
begin
  Select 'Value is not NULL' As Result
end
Example for "Temprory Table"

declare @ABC table(Col1 int, Col2 varchar(20))

insert into @ABC values(1,'Test 1')

insert into @ABC values(2,'Test 2')

insert into @ABC values(3,'Test 3')

insert into @ABC values(4,'Test 4')

insert into @ABC values(5,'Test 5')

insert into @ABC values(null,'Test 6')

insert into @ABC values(7,'Test 7')

insert into @ABC values(null,'Test 8')

insert into @ABC values(null,'Test 9')

insert into @ABC values(10,'Test 10')

--It returns 3 rows
select * from @Temp where Col1 in(1,3,6)

--It does not include null so it returns 3 rows 
select * from @Temp where Col1 in(1,3,6,null)

1). Use Ascending order

select * from @Temp order by Col1;

2). -- Use descending order

select * from @ABC order order by Col1 Desc

3).  Null in GroupBy

select col1 count(col2)
AS
from @ABC
Group By Col1

4). Case expression

select CASE when name IS NULL then 'N/A' else name end from Country
---where Country is a table---

5). Using COALESCE 

Select COALESCE(name, 'N/A') from Countries

6). ---Return 'N/A' if the name is NULL

Select IF(name IS NULL, 'N/A', name) from countries
About to NULL value's facts,

it is not equal to or similar as any value
it is not greater than, less than or different from any type of value
The null value is not equal to NULL itself.
it is not greater than, less than or different from NULL values.

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