In SQL, how does using DISTINCT affect performance?

Question

I am trying to select a separate list in which duplicates are created in multiple fields. For example,

SELECT tablename.field1Date, 
       tablename.field2Number, 
       tablename.field3Text 
FROM tablename;

Selection of duplicate entries by date, number and text fields, respectively.

Now that I select individual records to ensure what I'm looking for, performance seems to be drastically reduced.

SELECT DISTINCT tablename.field1Date,
                tablename.field2Number, 
                tablename.field3Text 
FROM tablename;

Are there any known reasons for this? I must admit that I am using MS Access 2003, and this can be a problem.

Answer 1

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Answer 2

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http://support.microsoft.com/kb/209126

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