When you want to replace a possibly null column with something else, use IsNull.
SELECT ISNULL(myColumn, 0 ) FROM myTable
This will put a 0 in myColumn if it is null in the first place.
Answer from phadaphunk on Stack OverflowVideos
When you want to replace a possibly null column with something else, use IsNull.
SELECT ISNULL(myColumn, 0 ) FROM myTable
This will put a 0 in myColumn if it is null in the first place.
You can use both of these methods but there are differences:
SELECT ISNULL(col1, 0 ) FROM table1
SELECT COALESCE(col1, 0 ) FROM table1
Comparing COALESCE() and ISNULL():
The ISNULL function and the COALESCE expression have a similar purpose but can behave differently.
Because ISNULL is a function, it is evaluated only once. As described above, the input values for the COALESCE expression can be evaluated multiple times.
Data type determination of the resulting expression is different. ISNULL uses the data type of the first parameter, COALESCE follows the CASE expression rules and returns the data type of value with the highest precedence.
The NULLability of the result expression is different for ISNULL and COALESCE. The ISNULL return value is always considered NOT NULLable (assuming the return value is a non-nullable one) whereas COALESCE with non-null parameters is considered to be NULL. So the expressions ISNULL(NULL, 1) and COALESCE(NULL, 1) although equivalent have different nullability values. This makes a difference if you are using these expressions in computed columns, creating key constraints or making the return value of a scalar UDF deterministic so that it can be indexed as shown in the following example.
-- This statement fails because the PRIMARY KEY cannot accept NULL values -- and the nullability of the COALESCE expression for col2 -- evaluates to NULL.
CREATE TABLE #Demo
(
col1 integer NULL,
col2 AS COALESCE(col1, 0) PRIMARY KEY,
col3 AS ISNULL(col1, 0)
);
-- This statement succeeds because the nullability of the -- ISNULL function evaluates AS NOT NULL.
CREATE TABLE #Demo
(
col1 integer NULL,
col2 AS COALESCE(col1, 0),
col3 AS ISNULL(col1, 0) PRIMARY KEY
);
Validations for ISNULL and COALESCE are also different. For example, a NULL value for ISNULL is converted to int whereas for COALESCE, you must provide a data type.
ISNULL takes only 2 parameters whereas COALESCE takes a variable number of parameters.
if you need to know more here is the full document from msdn.
Hello,
This is my query
SELECT ordertype, status, sum (COUNT (printdate)) over (), date(char(1900000+requestdate)), businessunit FROM Casepallet WHERE date(char(1900000+requestdate)) IN (current date, current date + 1 days) AND business unit=' SCS' AND ordertype!='T1' AND status = 'X' group by ordertype, business unit, request date, status, printdate order by printdate desc limit 1
Sometimes the sum/count of printdate returns nothing, it's null. If it's null I want it to return 0.
I tried doing it like this: COALESCE (sum (COUNT (printdate)) over (), 0), but it doesn't work, it still returns null.
Can anyone guide me here on where I go wrong?
As others have mentioned you forgot to tell your CASE statement to return the number in case the number is not null.
However in SQL Server you can use NULLIF, which I consider more readable:
select
id,
firstname,
lastname,
nullif(number, 0) as number
from tperson;
If you want to stick to standard SQL then stay with CASE:
case when number = 0 then null else number end as number
SELECT ID, Firstname, Lastname,
CASE WHEN Number!=0 THEN Number END
FROM tPerson