有一個表，用戶需要在後台操作它，希望能對它動態進行添加刪除字段。這個功能也許沒有問題，但是它原有插入與更新的兩個存儲過程，也需要一起修改。因此Insus.NET實現了它，因此此文會讓你了解到怎樣動態為一個表添加刪除字段以及動態修改它的存儲過程
首先需要建一個表[A]，這個表只有兩個字段，一個是[ID]自動增長,另一個是表[B]的字段名，存儲的每一筆記錄，即是用戶需要操作的表[B]的字段。這個表[A]需要建添加，更新，以及刪除的存儲過程，方便用戶在後台方便操作，還有重點部分，需要寫觸發器。如有記錄對表[A]進行添加，更新或是刪除時，它會觸發去作表[B]相應操作，還要去修改表[B]的存儲過程。
動態修改表[B]的存儲過程：
復制代碼 代碼如下:
CREATE PROCEDURE [dbo].[usp_B_DymanicallyAlterStoreProcedure]
AS
DECLARE @VariableList NVARCHAR(MAX) = ''
DECLARE @FieldList NVARCHAR(MAX) = ''
DECLARE @ValueList NVARCHAR(MAX) = ''
DECLARE @FieldValueList NVARCHAR(MAX) = ''
DECLARE @I INT = 1, @R INT = 0
SET @R = (SELECT MAX([Id]) FROM [dbo].[A])
WHILE (@I <= @R)
BEGIN
DECLARE @fName NVARCHAR(100)
IF EXISTS(SELECT [Id] FROM [dbo].[A] WHERE [Id] = @I)
BEGIN
SELECT @fName = [FieldName] FROM [dbo].[A] WHERE [Id] = @I
SET @VariableList = @VariableList + ',@' + @fName +' DECIMAL(18,4)' --動態的字段數據類型都一樣
SET @FieldList = @FieldList + ',[' + @fName + ']'
SET @ValueList = @ValueList + ',@' + @fName
SET @FieldValueList = @FieldValueList + ',[' + @fName + '] = @' + @fName
END
SET @I = @I + 1
END
DECLARE @sql_I NVARCHAR(MAX),@sql_U NVARCHAR(MAX)
SET @sql_I = '
ALTER PROCEDURE [dbo].[usp_B_Insert]
(
@ItemCode NVARCHAR(50)
'+ @VariableList +'
)
AS
INSERT INTO [dbo].[B] ([ItemCode]'+ @FieldList +') VALUES (@ItemCode'+ @ValueList +')
'
EXECUTE sp_EXECUTESQL @sql_I;
SET @sql_U = '
ALTER PROCEDURE [dbo].[usp_B_Update]
(
@Id INT,
@ItemCode NVARCHAR(50)
'+ @VariableList +'
)
AS
UPDATE [dbo].[B] SET [ItemCode] = @ItemCode'+ @FieldValueList +' WHERE [Id] = @Id
'
EXECUTE sp_EXECUTESQL @sql_U;
表[A]的插入觸發器：
復制代碼 代碼如下:
CREATE TRIGGER [dbo].[tri_A_Insert] ON [dbo].[A]
FOR INSERT
AS
BEGIN
SET NOCOUNT ON
DECLARE @FieldName NVARCHAR(50)
SELECT @FieldName = [FieldName] FROM INSERTED
EXECUTE('IF NOT EXISTS(SELECT * FROM SYSCOLUMNS WHERE [id] = OBJECT_ID(''B'') AND [name] = '''+ @FieldName +''')
ALTER TABLE [B] ADD ['+ @FieldName +'] DECIMAL(18,4) NULL')
EXECUTE [dbo].[usp_B_DymanicallyAlterStoreProcedure];
END
表[A]刪除觸發器：
復制代碼 代碼如下:
CREATE TRIGGER [dbo].[tri_A_Delete] ON [dbo].[A]
FOR DELETE
AS
BEGIN
SET NOCOUNT ON
DECLARE @FieldName NVARCHAR(50)
SELECT @FieldName = [FieldName] FROM DELETED
EXECUTE('IF EXISTS(SELECT * FROM SYSCOLUMNS WHERE [id] = OBJECT_ID(''B'') AND [name] = '''+ @FieldName +''')
ALTER TABLE [B] DROP COLUMN ['+ @FieldName +']')
EXECUTE [dbo].[usp_B_DymanicallyAlterStoreProcedure];
END
