How do I comment SQL code out in Microsoft Access?

As MathewMartin said, you can't. I use the following workaround:

SELECT * FROM x
WHERE "-- your comment. This plain string is always true";

SELECT * FROM x
WHERE y = 'something'
AND " -- z = 'something else' ";

No. You cannot have any extraneous text in Microsoft Access (JET-SQL).

You can make some constraints ignored, e.g.,

Where 
name = "joe"
OR
(state = "VA" AND 1=0)

But that technique is a rather limited way to hide existing SQL.

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