[Solved] How to select the SQL database values that has the same name and sum up their corresponded values [closed]

Question

You can group by Cattle

SELECT Cattle, SUM(Liter) AS TotalLiter
FROM NewMilk
GROUP BY Cattle
ORDER BY Cattle

See: SQL GROUP BY Statement

Or if you need the total of only one specific cattle type

SELECT SUM(Liter) AS TotalLiter
FROM NewMilk
WHERE Cattle="Cow"

You can execute a SQL command returning rows like this

string sql = "SELECT Cattle, SUM(Liter) AS TotalLiter ... "; // 1st SQL example.
using (var con = new SqlConnection("connection string"))
using (var cmd = new SqlCommand(sql, con)) {
    con.Open();
    var reader = cmd.ExecuteReader();
    while (reader.Read()) {
        string cattle = reader.GetString(0); // 1st column
        int total = reader.GetInt32(1); // 2nd column
        ...
    }
}

Or, if you have only one row with one column, i.e. one result value

string sql = "SELECT SUM(Liter) AS TotalLiter ... ";  // 2nd SQL example.
using (var con = new SqlConnection("connection string"))
using (var cmd = new SqlCommand(sql, con)) {
    con.Open();
    int total = (int)cmd.ExecuteScalar();
    ...
}

See also: The Right Way to Query a Database: Parameterizing your SQL Queries.

Accepted Answer