Coalesce Function

The COALESCE() function can take multiple arguments and return the first non-null value from the list of arguments. For example:

Select coalesce(null,'Hight',null,'Low') as 'coalesce function' 

The above query returns the second value because it considers the second value as the first value that isn’t null.

Replace Null with Empty String Using Coalesce Function

-- Replace Null with Empty string
select Company,[First Name],[Last Name], coalesce([E-mail Address],'') as email from [dbo].[Customers]

-- Replace Null with custom value
select Company,[First Name],[Last Name], coalesce([E-mail Address],'Email address missing') as email from [dbo].[Customers]

Result:

ISNULL Function

The ISNULL() function takes two arguments. It returns the not null value first. For example

Select ISNULL('Hight',null) as 'ISNULL function' 

Replace Null with Empty String Using ISNULL Function

select Company,[First Name],[Last Name], ISNULL([E-mail Address],'') as email from [dbo].[Customers]

Result

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