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Dblookupcombobox has a null string

I have a question about DBLookupComboBox.

I have a program in which there is a database that I wrote. It has everything, except when I open DBLookupComboBox, it should have a row with a zero value when the user wants to choose nothing. But there is no one. How can I show a null string?

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You should either add a line that says “Nothing” or “All” that ever fits. The usual solution is to query UNION, which can be used as a RowSource in a combo box. Union query can be used to add virtual fields.

If the combo contains only unique values, you can say:

SELECT "Nothing" As Description FROM ATable UNION SELECT Description FROM ATable

UNION removes duplicates, UNION ALL <no, so if there are matching rows, you can say:

 SELECT DISTINCT "Nothing" As Description FROM ATable UNION ALL SELECT Description FROM ATable

If you want Nothing to be sorted first, you should manipulate a bit and use Nothing or -Nothing, but if you have an ID column or Key, you can get a good look, for example:

 SELECT 0 As ID, "Nothing" As Description FROM ATable UNION SELECT ID, Description FROM ATable
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Source: https://habr.com/ru/post/917976/

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