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 OverflowWhen 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.
Use IFNULL:
IFNULL(expr1, 0)
From the documentation:
If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. IFNULL() returns a numeric or string value, depending on the context in which it is used.
None of the above answers were complete for me.
If your field is named field, so the selector should be the following one:
IFNULL(`field`,0) AS field
For example in a SELECT query:
SELECT IFNULL(`field`,0) AS field, `otherfield` FROM `mytable`
Hope this can help someone to not waste time.
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?
Most database servers have a COALESCE function, which will return the first argument that is non-null, so the following should do what you want:
SELECT COALESCE(SUM(Price),0) AS TotalPrice
FROM Inventory
WHERE (DateAdded BETWEEN @StartDate AND @EndDate)
Since there seems to be a lot of discussion about
COALESCE/ISNULL will still return NULL if no rows match, try this query you can copy-and-paste into SQL Server directly as-is:
SELECT coalesce(SUM(column_id),0) AS TotalPrice
FROM sys.columns
WHERE (object_id BETWEEN -1 AND -2)
Note that the where clause excludes all the rows from sys.columns from consideration, but the 'sum' operator still results in a single row being returned that is null, which coalesce fixes to be a single row with a 0.
You can use ISNULL().
SELECT ISNULL(SUM(Price), 0) AS TotalPrice
FROM Inventory
WHERE (DateAdded BETWEEN @StartDate AND @EndDate)
That should do the trick.
Use coalesce():
select coalesce(Eprice, 0) as Eprice
In SQL Server only, you can save two characters with isnull():
select isnull(Eprice, 0) as Eprice
Try these three alternatives:
1. ISNULL(MyColumn, 0)
2. SELECT CASE WHEN MyColumn IS NULL THEN 0 ELSE MyColumn END FROM MyTable
3. SELECT COALESCE(MyCoumn, 0) FROM MyTable
There is another way but it is not supported by most of the databases SELECT MyColumn + 0 This might work, but NULL + anything is still NULL in T-SQL.
You can use a CASE statement.
SELECT
CASE WHEN currate.currentrate IS NULL THEN 1 ELSE currate.currentrate END
FROM ...
You can use COALESCE:
SELECT orderhed.ordernum,
orderhed.orderdate,
currrate.currencycode,
coalesce(currrate.currentrate, 1) as currentrate
FROM orderhed
LEFT OUTER JOIN currrate
ON orderhed.company = currrate.company
AND orderhed.orderdate = currrate.effectivedate
Or even IsNull():
SELECT orderhed.ordernum,
orderhed.orderdate,
currrate.currencycode,
IsNull(currrate.currentrate, 1) as currentrate
FROM orderhed
LEFT OUTER JOIN currrate
ON orderhed.company = currrate.company
AND orderhed.orderdate = currrate.effectivedate
Here is an article to help decide between COALESCE and IsNull:
http://www.mssqltips.com/sqlservertip/2689/deciding-between-coalesce-and-isnull-in-sql-server/