About SQL data query statements

1、 The foundation is not solid enough , The sentences used are the following results

  <select id="relieveTotal" resultType="java.lang.Float">	  	
	SELECT SUM(SALES_AMOUNT) FROM TB_ORDER TR
	    WHERE TR.USER_ID = #{userId}
	    AND TR.SALES_TIME &gt;= TO_DATE(TO_CHAR(  
		    (SELECT  MAX(W.WKH_MTIME) 
		    	FROM TB_WKH W 
		    	WHERE W.USER_ID = #{userId} 
		    	AND W.WKH_DIR = 0 
		    	GROUP BY W.USER_ID ) ,  
		    	'YYYY-MM-DD' ) , 'YYYY-MM-DD' ) 
  </select>

How to add a column of data ( There is only one time value , It's part of the code above )

 SELECT MAX(W.WKH_MTIME) 
        FROM TB_WKH W 
        WHERE W.USER_ID = 2
        AND W.WKH_DIR = 0 
        GROUP BY W.USER_ID

Question 1 、
above 2 End code can get results , How to combine their results , Output ----- Become a row and two columns ( Decimal and time are in one column ) And the results of that come out ,
Who knows help

Question two 、
The previous code , Report errors :Cause: java.sql.SQLDataException: ORA-01861: Text does not match format string
What's the cause of the , Help me if you know , I don't know how to change it now :
At present, I can only adopt flexible methods ------ become resultMap Try your way

 <select id="relieveTotal" resultMap="total_result">	  	<!--  Change the returned data type   -->
	SELECT SUM(SALES_AMOUNT)    SALES_AMOUNT   <!--  Use a field of the same type for temporary storage  -->
	FROM TB_ORDER TR
	    WHERE TR.USER_ID = #{userId}
	    AND TR.SALES_TIME &gt;= TO_DATE(TO_CHAR(  
		    (SELECT  MAX(W.WKH_MTIME) 
		    	FROM TB_WKH W 
		    	WHERE W.USER_ID = #{userId} 
		    	AND W.WKH_DIR = 0 
		    	GROUP BY W.USER_ID ) ,  
		    	'YYYY-MM-DD' ) , 'YYYY-MM-DD' ) 
  </select>