How to select sum(max remain(x + y + z)) from
MySQL, to catch sum(1200+1300+1400)
?
id | user | remain
-----------------
1 | x | 1000
----------------
2 | x | 1200
----------------
3 | y | 1100
----------------
4 | y | 1300
----------------
5 | z | 1200
----------------
5 | z | 1400
----------------
using (SqlConnection cn = new SqlConnection(Class1.x))
{
cn.Open();
string cm1 = "select sum(max remain(all users)) as 'total' from item_new_company";
using (SqlCommand cmd = new SqlCommand(cm1, cn))
{
using (SqlDataReader dr = cmd.ExecuteReader())
{ dr.Read(); tot5 = dr["total"].ToString(); }
}
}
Like this:
SELECT SUM(MaxRemain) TotalOfMaxRemains
FROM
(
SELECT MAX(remain) AS MaxRemain
FROM item_new_company
GROUP BY user
) AS t;
The result:
| TOTALOFMAXREMAINS |
---------------------
| 3900 |
The subquery:
SELECT MAX(remain) AS MaxRemain
FROM item_new_company
GROUP BY user
with GROUP BY user
and MAX(remain)
, will give you the max of remain
for each user
, then in the outer query the SUM
will give you the total.
For SQL Server, the previous query should work fine, but there is another way to do so:
WITH CTE AS
(
SELECT *, ROW_NUMBER() OVER(PARTITION BY [user]
ORDER BY id DESC) AS rownum
FROM item_new_company
)
SELECT SUM(remain) AS Total
FROM CTE
WHERE rownum = 1;
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