通过比较同一表中的互斥值，从表中选择所有数据

Question

I have a Microsoft Access table as show below, Where Item 1 and Item 2 are mutually exclusive.

I need a query to generate the following result

1. Always retrieves all the entries of the table
2. If both Item 1 and Item 2 is present (manual editing of database is possible) only values of Item 2 will be returned in the result.
3. Original table should not be altered

What should I do?

Answer 1

You should use IIF(Condition, ValueIfTrue, ValueIfFalse) statement:

SELECT Id, IIF([Item 1] IS NOT NULL AND [Item 2] IS NOT NULL, NULL, [Item 1]) AS [Item 1], [Item 2]

FROM TableName

Office Support IIF Function

Answer 2

据我所知，最好将case语句与排名函数一起使用。