Not able to query with null values

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I need to query based on the parameter, used parameter in the CASE clause.

Parameter will contain these values : contactSuccess,contactFail,notcontacted

We have column : empCommunication which is boolean. It will take 0,1, null

Based on the Parameter value, I need to run the query.

Eg: if Parameter is contactSuccess then Where clause should be empCommunication = 1

if Parameter is contactFail then Where clause should be empCommunication = 0

The above two scenario's are working with the below query, but if fails with

Parameter is notContacted, in this case Where clause should be empCommunication IS NULL.

Kindly help me on this.

SELECT
        empCategory as name,
        count(*) as value
from EmployeeRecords R
WHERE empCommunication =
    CASE ?
        WHEN 'contactSuccess' THEN  1
        WHEN 'contactFail' THEN 0
        WHEN 'notcontacted' THEN  IS NULL
     END
group by empCategory

Use coalesce() to cover the case where the parameter is 'notcontacted' with a different value like -1:

SELECT
        empCategory as name,
        count(*) as value
from EmployeeRecords R
WHERE coalesce(empCommunication, -1) =
    CASE ?
        WHEN 'contactSuccess' THEN  1
        WHEN 'contactFail' THEN 0
        WHEN 'notcontacted' THEN -1
     END
group by empCategory

SQL NULL Values - IS NULL and IS NOT NULL, It is not possible to test for NULL values with comparison operators, such as =, < Select all records from the Customers where the PostalCode column is empty. 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 this field. Then, the field will be saved with a NULL value. Note: A NULL value is different from a zero value or a field that contains spaces.

Assume that your param is p_param, you could change your query to

SELECT
    empCategory AS name,
    COUNT(*) AS value
FROM EmployeeRecords
WHERE 
    (empCommunication IS NULL AND p_param = 'notcontacted')
    OR (empCommunication = 1 AND p_param = 'contactSuccess')
    OR (empCommunication = 0 AND p_param = 'contactFail')
GROUP BY empCategory;

SQL NULL Check in Where clause, We cannot use comparison operators such as =, <, > etc on null values because the result is SELECT column_name1, column_name2, column_name3, . Any comparison - equality, inequality, LIKE, greater or less than - to a NULL field returns NULL, and the record is not retrieved. Instead of a criterion such as. ( ( ( [Customer Contact List].Customer) Like (IIf ( [Forms]! [Customer Contact List Parameter Form]!

Try this one!

SELECT
        empCategory as name,
        count(*) as value
        from EmployeeRecords R WHERE empCommunication =
(CASE a_column_in_table
        WHEN 'contactSuccess' THEN  1
        WHEN 'contactFail' THEN 0
        WHEN 'notcontacted' THEN  NULL
        else null
 END)
group by empCategory;`

How to SELECT Records With No NULL Values in MySQL, How to SELECT Records With No NULL Values in MySQL that can be used to filter out database query results which may contain NULL or empty values,� NULL is not treated as a real value, you could rather call it "unknown". So if the value is unknown it is not clear if in your case state is 0, 1, or anything else. So NULL != 1 results to NULL again. This concludes that whereever you filter something that may be NULL, you have to treat NULL values by yourself.

SQL NULL Values, How do we select only the records with no NULL values in the "Address" column ? We will have to use the IS NOT NULL operator: SELECT LastName,FirstName, � To help with NULL handling, you can use the IS NULL and IS NOT NULL operators and the IFNULL() function. In SQL, the NULL value is never true in comparison to any other value, even NULL . An expression that contains NULL always produces a NULL value unless otherwise indicated in the documentation for the operators and functions involved in the

B.3.4.3 Problems with NULL Values, mysql> SELECT NULL, 1+NULL, CONCAT('Invisible',NULL);. To search for column values that are NULL , you cannot use an expr = NULL test. The following � You can follow best practices when developing your SQL Server database schema, but you still cannot eliminate all NULL values. The simple fact is that you have to allow NULL for some columns and some queries will return NULL values. The issue with NULL values is that not planning for them being included in your query results will lead to problems.

Once you decide that null values are acceptable, it's your job to accommodate them throughout the application. To find or exclude null values, use Is Null and Not Is Null, respectively, in criteria

Comments
  • It's generally better to use AND/OR constructions instead of case expressions in the WHERE clause.
  • THEN NULL instead of THEN IS NULL.
  • I tired it, it is not working, as it takes the where empCommunication = null instead of empCommunication is null. The problem is in parameter ( ? ) , I'm not getting values, i'm getting some lables based on that we need to modify the query.