如何按升序对列进行排序，最后将NULL值排序？

Question

I'm working on a personal database to track my projects.

I have a date/time column called StartDate in the table that I'm sorting in ascending order in the query that's used as the data source for the form where I'm entering data.

The form is a split form that displays the data in the "Detail" section in table format.

Until now, I have entered projects as they are assigned, but I have a need now to also track common projects that will be assigned but have not been assigned yet.

To track this, I wanted to enter the future projects without a start date.

However, when I enter the records like this, they are getting sorted to the top instead of at the bottom of the list where I prefer it.

Is there any way to override the sort so the records with a value in the StartDate column with sort ascending, but the records without a value in the StartDate column will sort at the end?

Thanks!

Answer 1

If you calculate anything on the date field, you'll loose the use of the index on that.

So check for Null :

SELECT 
    startdate, id
FROM 
    YourTable
ORDER BY
    StartDate Is Null,
    StartDate

Answer 2

A possibility would be to sort by this:

ORDER BY Nz([StartDate], CDate("31.12.2999"))

Here the function NZ is used to convert Null values ('on the fly', only in the query) to the date 31.12.2999 and so the sorting is as you want.

Answer 3

You can create a calculated field to order your data.

I did a simple table (named tbl ) with dates, some of them with blanks:

As you can see, rows with ID 4,5 and 9 are blanks in StartDate

Then I made up a query with a calculated field that will check if the field StartDate is not blank. If true, return 0, if false, return 1. That way all blank Startdate rows will return 1 and non blanks will return 0. Then order by this calculated field first and order by StartDate as second order field.

The formula of calculated field is: IIf(IsNull([StartDate])=False,0,1)

The SQL code of query is:

SELECT tbl.startdate, tbl.id
FROM tbl
ORDER BY IIf(IsNull([StartDate])=False,0,1), tbl.startdate

I get this as output:

As you can see, rows with ID 4,5 and 9 are blanks in StartDate , and they are at bottom of recordset.

Hope you can adap this to your needs.