SQL how to make null values come last when sorting ascending

问题

I have a SQL table with a datetime field. The field in question can be null. I have a query and I want the results sorted ascendingly by the datetime field, however I want rows where the datetime field is null at the end of the list, not at the beginning.

Is there a simple way to accomplish that?

回答1:

select MyDate from MyTable order by case when MyDate is null then 1 else 0 end, MyDate 

回答2:

(A "bit" late, but this hasn't been mentioned at all)

You didn't specify your DBMS.

In standard SQL (and most modern DBMS like Oracle, PostgreSQL, DB2, Firebird, Apache Derby, HSQLDB and H2) you can specify NULLS LAST or NULLS FIRST:

Use NULLS LAST to sort them to the end:

select * from some_table order by some_column DESC NULLS LAST 

回答3:

I also just stumbled across this and the following seems to do the trick for me, on MySQL and PostgreSQL:

ORDER BY date IS NULL, date DESC 

as found at https://stackoverflow.com/a/7055259/496209

回答4:

order by coalesce(date-time-field,large date in future) 

回答5:

You can use the built-in function to check for null or not null, as below. I test it and its working fine.

select MyDate from MyTable order by ISNULL(MyDate,1) DESC, MyDate ASC;

回答6:

If your engine allows ORDER BY x IS NULL, x or ORDER BY x NULLS LAST use that. But if it doesn't these might help:

If you're sorting by a numeric type you can do this: (Borrowing the schema from another answer.)

SELECT *           FROM Employees ORDER BY ISNULL(DepartmentId*0,1), DepartmentId; 

Any non-null number becomes 0, and nulls become 1, which sorts nulls last.

You can also do this for strings:

SELECT * FROM Employees ORDER BY ISNULL(LEFT(LastName,0),'a'), LastName 

Because 'a' > ''.

This even works with dates by coercing to a nullable int and using the method for ints above:

SELECT * FROM Employees ORDER BY ISNULL(CONVERT(INT, HireDate)*0, 1), HireDate 

(Lets pretend the schema has HireDate.)

These methods avoid the issue of having to come up with or manage a "maximum" value of every type or fix queries if the data type (and the maximum) changes (both issues that other ISNULL solutions suffer). Plus they're much shorter than a CASE.

回答7:

When your order column is numeric (like a rank) you can multiply it by -1 and then order descending. It will keep the order you're expecing but put NULL last.

select * from table order by -rank desc 

回答8:

SELECT *           FROM Employees ORDER BY ISNULL(DepartmentId, 99999); 

See this blog post.

回答9:

Thanks RedFilter for providing excellent solution to the bugging issue of sorting nullable datetime field.

I am using SQL Server database for my project.

Changing the datetime null value to '1' does solves the problem of sorting for datetime datatype column. However if we have column with other than datetime datatype then it fails to handle.

To handle a varchar column sort, I tried using 'ZZZZZZZ' as I knew the column does not have values beginning with 'Z'. It worked as expected.

On the same lines, I used max values +1 for int and other data types to get the sort as expected. This also gave me the results as were required.

However, it would always be ideal to get something easier in the database engine itself that could do something like:

Order by Col1 Asc Nulls Last, Col2 Asc Nulls First  

As mentioned in the answer provided by a_horse_with_no_name.

回答10:

In Oracle, you can use NULLS FIRST or NULLS LAST: specifies that NULL values should be returned before / after non-NULL values:

ORDER BY { column-Name | [ ASC | DESC ] | [ NULLS FIRST | NULLS LAST ] } 

For example:

ORDER BY date DESC NULLS LAST 

Ref: http://docs.oracle.com/javadb/10.8.3.0/ref/rrefsqlj13658.html

回答11:

order by -cast([nativeDateModify] as bigint) desc 

回答12:

Solution using the "case" is universal, but then do not use the indexes.

order by case when MyDate is null then 1 else 0 end, MyDate 

In my case, I needed performance.

 SELECT smoneCol1,someCol2    FROM someSch.someTab  WHERE someCol2 = 2101 and ( someCol1 IS NULL )    UNION     SELECT smoneCol1,someCol2  FROM someSch.someTab  WHERE someCol2 = 2101 and (  someCol1 IS NOT NULL)   

回答13:

If you're using MariaDB, they mention the following in the NULL Values documentation.

Ordering

When you order by a field that may contain NULL values, any NULLs are considered to have the lowest value. So ordering in DESC order will see the NULLs appearing last. To force NULLs to be regarded as highest values, one can add another column which has a higher value when the main field is NULL. Example:

SELECT col1 FROM tab ORDER BY ISNULL(col1), col1; 

Descending order, with NULLs first:

SELECT col1 FROM tab ORDER BY IF(col1 IS NULL, 0, 1), col1 DESC; 

All NULL values are also regarded as equivalent for the purposes of the DISTINCT and GROUP BY clauses.

The above shows two ways to order by NULL values, you can combine these with the ASC and DESC keywords as well. For example the other way to get the NULL values first would be:

SELECT col1 FROM tab ORDER BY ISNULL(col1) DESC, col1; --                                         ^^^^ 

回答14:

USE NVL function

  select * from MyTable order by NVL(MyDate, to_date('1-1-1','DD-MM-YYYY')) 

Here's the alternative of NVL in most famous DBMS

来源：https://stackoverflow.com/questions/1498648/sql-how-to-make-null-values-come-last-when-sorting-ascending