CODEWITHSUNDEEP
sql
user993935
user993935

Reputation: 3903

SQL NULL Condition

I'm new to development. In sql I have written a stored procedure and it is working correctly but I just wanted to make sure it is done the correct way.

Here I am using an IF statement in sp to check whether date column in a table is NULL or not:

  if ((select sdate 
       from tbla 
         where id='3') = Null)
begin
  some query
end

Will this work for all cases or do I need to check for ''(empty) also?

Upvotes: 2

Views: 1604

Answers (3)

AaronLS
AaronLS

Reputation: 38392

If you want to display some other expression whenever something is null, Coalesce may be what you want.

Select CASE When (null = null) Then 1 Else 0 END

Result: 0

Select CASE When (null is null) Then 1 Else 0 END

Result: 1

Select null + 'soemthing'

Result: null

Select Coalesce(null, 'DefaultValueIfNull')

Result: DefaultValueIfNull

Append a space and last name only if lastname is not null:

select FirstName + coalesce(' ' + LastName, '') From People

Append a space and last name only if lastname is not null, with handling for empty LastName:

select FirstName + coalesce(' ' + CASE LastName When '' Then null Else LastName END, '') From People

Upvotes: 3

Shaun
Shaun

Reputation: 2476

Empty and NULL are not the same thing, so you will need to check for an empty string separately. You also should use is null rather than = null to check if a column is null.

Upvotes: 4

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 727067

In SQL null is not equal to anything, including other nulls. You need to use is null instead of the = operation.

Upvotes: 11

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