Question

我有一个名为tblCar的表，有ID，CarNumber和其他32个字段。 32列填充为s1,s2,s3,.......,s32，因为它们专门用于说明它是否适用于SEATS（A），预订（B）和售出（S）。

我想计算该数据库的可用座位，预订座位和售罄座位。我该怎么写一个查询？

无论如何要从数据库中32个不同列的字符串S，B和A进行计数？

我想表现的是...... S = 20，B = 10，A = 2;

SqlCommand cmd = new SqlCommand(
  "Select count(*) 
   FROM tblCar 
   WHERE s1= 'S' or s2= 'S' or s3= 'S' 
   or s4= 'S' or s5= 'S' or s6= 'S' 
   or s7= 'S' or s8= 'S' or s9= 'S' 
   or s10= 'S' or s11= 'S' or s12= 'S' 
   or s13= 'S' or s14= 'S' or s15= 'S' 
   or s16= 'S' or s17= 'S' or s18= 'S' 
   or s19= 'S' or s20= 'S' or s21= 'S' 
   or s22= 'S' or s23= 'S' or s24= 'S' 
   or s25= 'S' or s26= 'S' or s27= 'S' 
   or s28= 'S' or s29= 'S' or s30= 'S' 
   or s31= 'S' or s32= 'S' ", con
); 
count += cmd.ExecuteNonQuery();

这就是我为“Sold”字段工作的方式。但它只显示count = -128.i将计数初始化为0

Answer 1

试试这个SQL查询：

SELECT SUM(CASE WHEN State = 'S' THEN 1 ELSE 0 END) AS Sold
, SUM(CASE WHEN State = 'B' THEN 1 ELSE 0 END) AS Booked
, SUM(CASE WHEN State = 'A' THEN 1 ELSE 0 END) AS Available
FROM 
    (SELECT S1, S2, S3, S4, S5, S6
    FROM Seats) s
UNPIVOT
    (State FOR Seat IN (S1, S2, S3, S4, S5, S6)) AS rows;

此处SQL Fiddle。

在示例中，我只使用了6列，但在您的情况下，您需要为所有32列设置，但只需要一次

C＃代码：

using SqlConnection conn = new SqlConnection(yourConnectionString)
{
    StringBuilder query = new StringBuilder();
    query.AppendLine("SELECT SUM(CASE WHEN State = 'S' THEN 1 ELSE 0 END) AS Sold");
    query.AppendLine(", SUM(CASE WHEN State = 'B' THEN 1 ELSE 0 END) AS Booked");
    query.AppendLine(", SUM(CASE WHEN State = 'A' THEN 1 ELSE 0 END) AS Available");
    query.AppendLine("FROM ");
    query.AppendLine("(SELECT S1, S2, S3, S4, S5, S6, S7, S8");
    query.AppendLine("(,S9, S10, S11, S12, S13, S14, S15, S16");
    query.AppendLine("(,S17, S18, S19, S20, S21, S22, S23, S24");
    query.AppendLine("(,S25, S26, S27, S28, S29, S30, S31, S32");
    query.AppendLine("FROM Seats) s");
    query.AppendLine("UNPIVOT");
    query.AppendLine("(State FOR Seat IN (S1, S2, S3, S4, S5, S6, S7, S8");
    query.AppendLine("(,S9, S10, S11, S12, S13, S14, S15, S16");
    query.AppendLine("(,S17, S18, S19, S20, S21, S22, S23, S24");
    query.AppendLine("(,S25, S26, S27, S28, S29, S30, S31, S32)) AS rows;");

    conn.Open();
    using SqlCommand command = new SqlCommand(query.ToString(), conn)
    {
        DataTable data = new DataTable();
        data.Load(command.ExecuteReader());
        //then get your values
        Int32 avialable = 0;
        Int32 booked= 0;
        Int32 sold = 0;
        if(data.Rows.Count > 0)
        {
            available = (Int32)data(0)("Available");
            booked = (Int32)data(0)("Booked");
            sold = (Int32)data(0)("Sold");
        }           
    }
}

Answer 2

如果希望它返回值，则应使用ExecuteScalar。

SqlCommand cmd = new SqlCommand("Select count(*) FROM tblCar WHERE s1= 'S' or s2= 'S' or s3= 'S' or s4= 'S' or s5= 'S' or s6= 'S' or s7= 'S' or s8= 'S' or s9= 'S' or s10= 'S' or s11= 'S' or s12= 'S' or s13= 'S' or s14= 'S' or s15= 'S' or s16= 'S' or s17= 'S' or s18= 'S' or s19= 'S' or s20= 'S' or s21= 'S' or s22= 'S' or s23= 'S' or s24= 'S' or s25= 'S' or s26= 'S' or s27= 'S' or s28= 'S' or s29= 'S' or s30= 'S' or s31= 'S' or s32= 'S' ", con); 
count += (int)cmd.ExecuteScalar();

Answer 3

由于您要返回1个值，因此应调用.ExecuteScalar。 Upi还需要将返回值转换为int。

count = Convert.ToInt32(sqlcmd01.ExecuteScalar());

来自MSDN

执行查询，并返回查询返回的结果集中第一行的第一列。其他列或行将被忽略。

您只需要查找1个值，因此只需致电cmd.ExecuteScalar(); ExecuteNonQuery()，ExecuteReader()更适合其他事情。（例如ExecuteNoNQuery()的{{1}}）

This SO Link很好地总结了这些差异。

Answer 4

你有一个非常令人讨厌的表格结构，我会考虑改变它，但你得到了你可以做到这一点：

    SELECT SUM(CASE s1 WHEN 'S' THEN 1 ELSE 0 END) as sold,
     SUM(CASE s1 WHEN 'A' THEN 1 ELSE 0 END) as available,
     SUM(CASE s1 WHEN 'B' THEN 1 ELSE 0 END) as booked,
   FROM tblCar 
   UNION
    SELECT SUM(CASE s2 WHEN 'S' THEN 1 ELSE 0 END),
     SUM(CASE s2 WHEN 'A' THEN 1 ELSE 0 END),
     SUM(CASE s2 WHEN 'B' THEN 1 ELSE 0 END),
   UNION
    ... Repeat the above for each field.... yuck!...
   UNION
   SELECT SUM(CASE s32 WHEN 'S' THEN 1 ELSE 0 END),
     SUM(CASE s32 WHEN 'A' THEN 1 ELSE 0 END),
     SUM(CASE s32 WHEN 'B' THEN 1 ELSE 0 END)

Answer 5

我个人的建议是重新设计表格。仅使用3列，“可用”，“已售出”和“预订”。每列保持和int（bigint可能？），int将把具有该条件的所有席位的状态保存为二进制代码。例如，如果座位1,2,3和4是唯一的'已售出'座位，价值变为1 + 2 + 4 + 8 = 17.如果仅座位4＆amp; 5是“卖出”的价值将是8 + 16 = 24.这样你就不必查询所有列来查找卖出的座位，你只需要查询“已售出”列，它就会告诉你哪些座位是出售。

来自数据库中不同列的数据计数

5 个答案: