來自數據庫中不同列的數據計數

Question

我有一個名爲tblCar的表，其中有ID,CarNumber等32個字段。 32列填寫爲s1,s2,s3,.......,s32，因爲它們專用於說明是否適用於可用（A），預訂（B）和已售出（S）的SEATS。

我想計算可用座位，預訂座位並從該數據庫中售完座位。 我該如何寫一個查詢？

無論如何，從字符串S，B和A從數據庫中的32個不同列數？我想展示的就是那樣..... 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(); 

這是我的「已售出」的工作field.but它顯示只算= -128.i並初始化計數爲0

Answer 1

，如果你希望它返回一個值，你應該使用的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 2

由於您要返回1值，因此應撥打.ExecuteScalar。 Upi也需要將返回值轉換爲int。

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

從MSDN

執行查詢，並在查詢返回的結果集返回第一行的第一列。其他列或行將被忽略。

你只找1個值，只需調用cmd.ExecuteScalar();ExecuteNonQuery()和ExecuteReader()是其他事情做得更好。 （對於INSERTS，例如ExecuteNoNQuery()）

This SO Link總結了很好的差異。

Answer 3

你有一個非常討厭的表結構和我想看看那個改變，但你有什麼，你可以這樣做：

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 4

試試這個SQL查詢：

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; 

這裏SQL Fiddle。

在例子中，我只用6列，但在你的情況，你需要爲所有32列集，但只有一次

C＃代碼：

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 5

我個人的建議是的重新設計表。只使用3列，'可用'，'出售'和'預訂'。每列保存並且int（bigint也許？），int將把所有具有該條件的位置的狀態保存爲二進制代碼。例如，如果座位1,2,3是唯一的「售出」座位，其價值變成1 + 2 + 4 + 8 = 17。如果僅座位4「& 5」被售出，則價值將是8 + 16 = 24。通過這種方式，您不必查詢所有列以查找已售座位，只需查詢「已售出」列，即可查詢哪些座位已售出 。