How do I find the tags that were applied by a particular user

The script below will provide fileids and tags applied by a particular user. You have to provide user name in the where clause.

SELECT * FROM 

    ( 
    SELECT 
    th.Fileid AS FileId, t.TagName, fi.RelativeFilePath, th.DirectHit, 
    tal.TagOrUntagType, tal.TagedOrUntaggedFromModule,     ui.UserName, 
    tal.TagAppliedDate AS ActionDateTime, rsi.Name AS ReviewSetName        
    FROM 
    tbl_ex_TagHistory th 
    INNER JOIN 
    tbl_ex_tag t 
               ON 
    th.Tagid = t.TagID 
    INNER JOIN 
    tbl_ex_FileInfo fi 
               ON 
    th.Fileid = fi.FileId 
               INNER JOIN 
    tbl_Ex_TagActionLog tal 
               ON 
    th.BatchID = tal.BatchID 
        AND th.Tagid = tal.TagID 
    LEFT JOIN 
    tbl_pj_userinfo ui 
    ON 
    tal.TagOrUntaggedBy = ui.UserID 
               LEFT JOIN 
    tbl_rev_ReviewBatch rb 

    ON 
               tal.ReviewBatchID = rb.BatchId 
    LEFT JOIN 
               tbl_rev_ReviewSetInfo rsi 

    ON 
               rb.ReviewSetId = rsi.ReviewSetId 

    ) T 
    where UserName = 'super' --replace with your user names
    ORDER BY FileId ASC, ActionDateTime DESC -- You can modify ordering, grouping, filtering etc. based on your need