用SQL完成條件式查詢--[收藏-From 黃偉榮]

因為覺得每次要用條件式查詢很煩(如範例一)，就想有沒有更方便的用法，試出一種方法還不錯，分享給大家。

測試環境

DBMS:Sql Server 2008 Express

DB:AdventureWorks

Table:Sales.SalesOrderDetail(Count:121,317)

 

情境

對Sales.SalesOrderDetail的OrderId與ProduceId與SaleDate這三個欄位做查詢(如圖一)，如果沒有輸入條件為顯示全部。

 

圖一 查詢畫面

 

範例一 傳統的條件式

   1:  StringBuilder sb = new StringBuilder();

   2:   

   3:  if (!string.IsNullOrEmpty(Order.Text))

   4:      sb.AppendFormat("SalesOrderID='{0}'", Order.Text);

   5:   

   6:  if (!string.IsNullOrEmpty(Produce.Text))

   7:  {

   8:      if (sb.Length > 0)

   9:          sb.Append(" AND ");

  10:   

  11:      sb.AppendFormat("ProductID='{0}'", Produce.Text);

  12:  }

  13:   

  14:  if (!string.IsNullOrEmpty(StartDate.Text))

  15:  {

  16:      if (sb.Length > 0)

  17:          sb.Append(" AND ");

  18:   

  19:      sb.AppendFormat("ModifiedDate > '{0}'", StartDate.Text);

  20:  }

  21:   

  22:  if (!string.IsNullOrEmpty(EndDate.Text))

  23:  {

  24:      if (sb.Length > 0)

  25:          sb.Append(" AND ");

  26:   

  27:      sb.AppendFormat("ModifiedDate < '{0}'", EndDate.Text);

  28:  }

  29:   

  30:  if (sb.Length > 0)

  31:      sb.Insert(0, " WHERE ");

  32:   

  33:  sb.Insert(0,"SELECT * FROM Sales.SalesOrderDetail");

如果是以前的我，我會這樣寫，落落長看的都累了，下一個範例展表直接在SQL中作掉。

 

範例二 更方便的寫法

   1:  string sql = string.Format("SELECT * FROM Sales.SalesOrderDetail WHERE" +

   2:                             "('{0}' = '' OR SalesOrderID = '{0}') AND " +

   3:                             "('{1}' = '' OR ProductID = '{1}') AND " +

   4:                             "('{2}' = '' OR ModifiedDate > '{2}') AND " +

   5:                             "('{3}' = '' OR ModifiedDate < '{3}')",

   6:                             Order.Text, Produce.Text, StartDate.Text, EndDate.Text);

這個方法是不是寫起來簡單，看起來乾淨，其作用為('' = '' OR SalesOrderID = '')參數是空的不查詢，('12345' = '' OR SalesOrderID = '12345')參數不是空的執行查詢。

 

應用一 SqlDataSource中使用

   1:  <asp:SqlDataSource ID="SqlDataSource" runat="server" CancelSelectOnNullParameter="false"

   2:  SelectCommand="SELECT * FROM Sales.SalesOrderDetail WHERE

   3:                (@Order IS NULL OR SalesOrderID = @Order) AND 

   4:                (@Produce IS NULL OR ProductID = @Produce) AND 

   5:                (@StartDate IS NULL OR ModifiedDate > @StartDate) AND 

   6:                (@EndDate IS NULL OR ModifiedDate < @EndDate)">

   7:  <SelectParameters>

   8:      <asp:ControlParameter ControlID="Order" Name="Order" ConvertEmptyStringToNull="true" />

   9:      <asp:ControlParameter ControlID="Produce" Name="Produce" ConvertEmptyStringToNull="true"/>

  10:      <asp:ControlParameter ControlID="StartDate" Name="StartDate" ConvertEmptyStringToNull="true"/>

  11:      <asp:ControlParameter ControlID="EndDate" Name="EndDate" ConvertEmptyStringToNull="true"/>

  12:  </SelectParameters>

  13:  </asp:SqlDataSource>

用這個方式，在DataSource中也可以做到DataSource條件式查詢，使用CancelSelectOnNullParameter=”false”，不管有沒有結果都要執行，因為設定ConvertEmptyStringToNull="true"，所以SQL中也可以使用(@Order IS NULL OR SalesOrderID = @Order)

 

應用二 StoreProcedure中使用

   1:  CREATE PROCEDURE SearchSalesOrderDetail

   2:      @Order varchar(10) = null ,

   3:      @Produce varchar(10) = null,

   4:      @StartDate datetime = null,

   5:      @EndDate datetime = null

   6:  AS

   7:  BEGIN

   8:  SELECT * FROM Sales.SalesOrderDetail WHERE

   9:  (@Order IS NULL OR SalesOrderID = @Order) AND 

  10:  (@Produce IS NULL OR ProductID = @Produce) AND 

  11:  (@StartDate IS NULL OR ModifiedDate > @StartDate) AND 

  12:  (@EndDate IS NULL OR ModifiedDate < @EndDate)

  13:  END

  14:  GO

當然也可以寫成Store Procedure直接在資料庫操作。

 

效能測試

各位最擔心的還是效能，就測試結果來說效能比較差，不過這樣物件導向是一樣的，為了方便多少會犧生一些效能，能不能接受，就看各位了。

 

EXEC dbo.SearchSalesOrderDetail NULL,NULL,NULL,NULL

 

 

 

 

SELECT * FROM Sales.SalesOrderDetail

 

 

EXEC dbo.SearchSalesOrderDetail '43659','776'

 

SELECT * FROM Sales.SalesOrderDetail WHERE SalesOrderID = '43659' AND ProductID = '776'