如何在SQL中的查询中创建一列的SUM？

I have one table with multiple columns. I am needing to create an SQL query to display certain columns based off of the user input from a datepicker and a select box. I have done that just fine. However, I am needing one of the result columns to be totaled at the bottom of the display table. I cannot figure out how to create a result within my current query to display the totaled column. Essentially, I would like the WTTotal column to be totaled into a separate cell. My current query is below. I really think this is something simple that I just can't seem to see.

SELECT REPLACE(Client,',',' ') AS Client,WorkTicketNum,Lease,Date,OrderedBy,WTTotal 
FROM WorkTicket 
WHERE Date BETWEEN '2014-10-01' AND '2014-10-31' AND Invoiced IS NULL 
ORDER BY Client 

SELECT REPLACE(Client,',',' ') AS Client,WorkTicketNum,Lease,Date,OrderedBy,WTTotal 
FROM WorkTicket 
WHERE Date BETWEEN '2014-10-01' AND '2014-10-31' AND Invoiced IS NULL 
ORDER BY Client 
UNION ALL
SELECT 'Total', NULL, NULL, NULL, NULL, SUM(WTTotal)
FROM WorkTicket
WHERE Date BETWEEN '2014-10-01' AND '2014-10-31' AND Invoiced IS NULL;

You can't have it with a single query. Putting a SUM() into your query would require a GROUP BY clause and collapse all of your original result rows down into a single result row - meaning your table would disappear. What you want a is a client-side solution. e.g. Start a counter in your client code and manually add up the results. In pseudoish-code:

$sum = 0;
while( $row = fetch_from_db() ) {
   $sum += $row['field_to_sum'];
   display_row();
}
echo "Total: $sum";

If you want to have it in a separate column, not in a separate row, either you calculate it in a subquery and join it to your result:

SELECT REPLACE(Client,',',' ') AS Client,WorkTicketNum,Lease,Date,OrderedBy, my_calculated_sum AS WTTotal 
FROM WorkTicket
JOIN (SELECT SUM(whatever_you_want_to_sum) as my_calculated_sum FROM WorkTicket) subquery_alias
WHERE Date BETWEEN '2014-10-01' AND '2014-10-31' AND Invoiced IS NULL 
ORDER BY Client 

Or you just calculate it with variables, like a running total. Your result is in the last row of the column.

SELECT REPLACE(Client,',',' ') AS Client,WorkTicketNum,Lease,Date,OrderedBy, @sum_variable := @sum_variable + whatever_you_want_to_sum AS WTTotal 
FROM WorkTicket 
, (SELECT @sum_variable := 0) var_init_subquery
WHERE Date BETWEEN '2014-10-01' AND '2014-10-31' AND Invoiced IS NULL 
ORDER BY Client 

But actually Kevin's solution is very good.

I also have similar solution as Kevin's :

;with cte_result
as 
(
    SELECT REPLACE(Client,',',' ') AS Client,WorkTicketNum,Lease,Date,OrderedBy,WTTotal 
    FROM   WorkTicket 
    WHERE  Date BETWEEN '2014-10-01' AND '2014-10-31' AND Invoiced IS NULL 
)
select * 
from   cte_result
union
select 'TotalAmount',NULL,NULL,NULL,NULL,sum(WTTotal)
from   cte_result
order  by client

but this solution will work only if your DB Engine supports CTE. with a CTE, we can use same resultset to get total's row.