SQL - Include where condition if variable is not null

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I am trying to add a where condition to be checked only if variable @schoolId is not null otherwise return all results. Please know that If condition cannot be used because it is a very large query. This is just a part of it.

Table Name - Students

Id Name   SchoolId
1  John      6
2  Mark      6
3  Alice     12
4  Prince   null

Query

Select * from Students st
where st.SchoolId = Case when @schoolId  is not null then @schoolId else st.SchoolId End

So if @schoolId is null, I want to return all 4 rows. I want it to return results where SchoolId is null too if variable is null. Currently with above query it does not return 4th row

You can use Boolean logic instead of case expression :

where (@schoolId is null) or
      (st.SchoolId = @schoolId);

SQL: IS NOT NULL Condition, The IS NOT NULL condition is used in SQL to test for a non-NULL value. If you are unable to support us by viewing our advertisements, please consider from the products table where the customer_id does not contain a NULL value. SQL Query to Select All If Parameter is NULL Example 3. In this example, we are using the IF-ELSE statement. If the parameter value is not null, we are using Select statement along with Where Clause, otherwise, no Where clause

Simply use or:

where (st.SchoolId = @schoolId or @schoolId is null)

You have two separate conditions and this checks both of them.

Is there a way to make a null check on a variable in a WHERE , One way is to use dynamic SQL, using a null check to optionally add that part of the where clause. 'select * from myTable where 1=1' if @myIdParam is not null set @vc_dynamicsql = @vc_dynamicsql + ' and myTable. If FirstName is NULL it will include all possible firstnames. If FirstName is '' then it will pull in everything where "FirstName Like '%%'" which also pulls everything in. In order to screw it up they'd have to type a space. You LTRIM (RTRIM ()) the FirstName to compensate for this, but this is correct.

Check this out:

declare @schoolId int

If @schoolId is null
Select * 
from dbo.Students st
Else
Select * 
from dbo.Students st
where st.SchoolId = @schoolId

SQL WHERE IS NULL, SELECT WHERE IS NOT NULL, NULL or , SQL IS NULL Clause. What is NULL and how do I query for NULL values? NULL is a special value that signifies 'no value'. Comparing a column to NULL using� You could use IS NULL: IF @varCHAR IS NULL AND @bit = 0 BEGIN RAISERROR ('varchar was not specified', 16,1); END Another approach is: DECLARE @varCHAR VARCHAR(MAX) = NULL; IF ISNULL(@varCHAR,'false') = 'false' AND @bit = 0 RAISERROR ('varchar was not specified', 16,1);

SQL NULL Values - IS NULL and IS NOT NULL, A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to� If you want to count any string consisting entirely of spaces as empty WHERE COLUMN <> '' Both of these will not return NULL values when used in a WHERE clause. As NULL will evaluate as UNKNOWN for these rather than TRUE.

If Variable is Blank Then No Where Clause – SQLServerCentral, dynamic sql for sure would solve this however this is not normally a good option. can you provide a little more detail on what you are trying to� Internally a value of NULL is an unknown value and therefore SQL Server does not equate an unknown value being equal to another unknown value. Another design decision is to not allow NULL values and therefore you will not run into these issues. Next Steps. When dealing with NULL values don't forget about the ISNULL function Be aware when

How to check for Is not Null And Is not Empty string in SQL server , 1: If you just want to match " " as an empty string, then use the WHERE clause like this: WHERE DATALENGTH(COLUMN) > 0. 2: But, if you� If expression is NOT a NULL value, the condition evaluates to TRUE. If expression is a NULL value, the condition evaluates to FALSE. Example - With SELECT Statement Here is an example of how to use the Oracle IS NOT NULL condition in a SELECT statement:

Comments
  • This won't work because it will only return null value if schoolId is not provided
  • . . . No, it will return all rows when @schoolId has no value.
  • @LearnAspNet. . . In your query with case expression, it will return 3 rows only when @schoolId is null. because null = null will evaluate as false.
  • This won't work because it won't return the 3rd row if SchoolId is not provided
  • @LearnAspNet . . . This does exactly what you are asking for. Why would you say the 3rd row would not be returned? This returns ALL rows when @schoolid is null.
  • Sorry, my bad. if you edit your answer in any way. I can upvote you. It does not let me change the vote