Your error may be cause by the last comma in the select statement. I just noticed that I had the extra comma in my sample.
If you google 'SQL Decode' you will find many examples. The syntax is: decode( expression , search , result [, search , result]... [, default] )
Don't quote me verbatim but in your example you could use something like: Select decode('[REQD.P.APPROACH]'='MICRO', 'Y', 'N'), ('[REQD.P.APPROACH]'='MICRO', 'Yes', 'No') from dual (this assumes that you would update your Dependency condition to 'Any Value' and would only update one field in your Results section).
Just remember that there is a limit to the number of characters you can use in the Logic section.