incorrect syntax near '='
<p>The following SQL generates the error "incorrect syntax near '=' The issue seems to be with the select statement (alias TITER).  I've swapped out the TITER Select statement with other tables, and the SQL executes without the error. The error will not generate after I add the FULL OUTER JOIN; only after I type TITER.FLDDATE = TITER.FLDDATE in the SELECT statement in the CROSS APPLY section. My goal is to isolate for the reason for the error and correct the syntax if needed.</p>

<pre><code>SELECT
    EMPLOYEE.FLDLNAME, 
    EMPLOYEE.FLDFNAME,
    EMPLOYEE.FLDREC_NUM,
    EMPLOYEE.FLDID2,
    TUBER_FLDDATE as "TUBER Date",
    TUBER_FLDCLASS as "TUBER Result",
    TITER.FLDDATE as "Titer Date"
FROM   EMPLOYEE 
CROSS APPLY
    (SELECT TUBER_FLDDATE = TUBER.FLDDATE,
            TUBER_FLDCLASS = TUBER.FLDCLASS,
            TITER.FLDDATE = TITER.FLDDATE
      FROM (SELECT rn = row_number() over(order by TUBER.FLDDATE),
              TUBER.FLDDATE, TUBER.FLDCLASS
            FROM TUBER 
            WHERE EMPLOYEE.FLDREC_NUM = TUBER.FLDEMPLOYEE
              and TUBER.FLDEMPLOYEE = '123') TUBER
        FULL OUTER JOIN 
            (Select rn = row_number() over(order by TITER.FLDDATE), 
                    TITER.FLDDATE 
             FROM TITER
             WHERE TITER.FLDTYPE = 'BAMT'
                AND EMPLOYEE.FLDREC_NUM = TITER.FLDEMPLOYEE
                and TITER.FLDEMPLOYEE = '123') TITER
           ON TITER.rn = TUBER.rn) tests
</code></pre>