今天上午因工作需要, 寫了一個(gè)在SQL Server中批量修改字段類型的小程序, 功能不是很完善, 尚未考慮字段的默認(rèn)值.但該程序涉及到了修改主鍵的字段類型, 修改有默認(rèn)值的字段跟修改主鍵字段的類型原理是一樣的.這裡只是對(duì)有默認(rèn)值的字段修改提供一些參考, 如果有興趣自己可以完善.
關(guān)於修改有默認(rèn)值的字段的一些參考資料
/*
從SysColumns表中cdefault字段是否為0可以判斷出是否有默認(rèn)值
查詢出字段的默認(rèn)值
Select text From SysComments
Where id = (Select cdefault from SysColumns where name = '字段')
修改有默認(rèn)值的字段時(shí)要先將對(duì)就的Default or DEFAULT constraint先刪除才行, 當(dāng)然在修改完字段時(shí)要重建啦.
Select Name From SysObjects Where xType = 'D'
and Parent_Obj = (Select id From SysObjects Where Name = '表名')
*/
程序代碼如下:
/*
此程序沒有考慮字段的默認(rèn)值
*/
-- xtype = '167' 字段類型為 varchar 可用 select * from systypes 查看
Declare curAlterInfo Cursor For Select a.Name AlterFieldName, a.Length, a.IsNullable, b.Name AlterTableName
From SysColumns a, SysObjects b Where a.id = b.id and a.xType = '167'
and b.xType = 'u' and a.cdefault = 0
declare @AlterFieldName nvarchar(50), -- 修改的字段
@AlterTableName nvarchar(50), -- 修改的表名
@Length int, -- 字段以長度
@IsNullable bit, -- 字段是否允許為空
@PkName nvarchar(50), -- 主鍵名
@PkFieldName nvarchar(500), --主鍵字段名
@TmpFieldName nvarchar(50),
@TmpTableName nvarchar(50),
@Sql nvarchar(500)
Set NoCount On
Begin Tran
open curAlterInfo
Fetch curAlterInfo Into @AlterFieldName, @Length, @IsNullable, @AlterTableName
While @@Fetch_Status=0
Begin
print @AlterTableName
--檢查修改的表是否有主鍵
If Exists(Select Name From SysObjects Where xType = 'PK'
and Parent_Obj = (Select id From SysObjects Where Name = @AlterTableName))
Begin
Set @TmpTableName = @AlterTableName
-- 取得主鍵名
Select @PkName = Name From SysObjects Where xType = 'PK'
and Parent_Obj = (Select id From SysObjects Where Name = @AlterTableName)
Set @PkFieldName = ''
-- 主鍵字段
Declare curPkFieldName Cursor For Select b.Name From SysIndexKeys a, SysColumns b
Where a.id = (Select id From SysIndexes Where Name = @PkName)
and a.indid = 1 and a.colid = b.colid and a.id = b.id
-- 取得所有的主鍵字段
Open curPkFieldName
Fetch curPkFieldName Into @TmpFieldName
While @@fetch_status = 0
Begin
Set @PkFieldName = @PkFieldName + @TmpFieldName + ','
Fetch curPkFieldName Into @TmpFieldName
End
Close curPkFieldName
Deallocate curPkFieldName
-- 刪除舊主鍵
Set @Sql = 'ALTER TABLE '+ @AlterTableName + ' DROP CONSTRAINT ' + @PkName
Print @Sql
Exec(@Sql)
end
-- 修改字段
Set @Sql = 'ALTER TABLE ' + @AlterTableName + ' ALTER COLUMN ' + @AlterFieldName
+ ' NVARCHAR( ' + CAST(@Length AS NVARCHAR) + ')'
-- 是否允許為空
if @IsNullable = 0
Set @Sql = @Sql + ' NOT NULL'
Print @sql
Exec(@sql)
Fetch curAlterInfo Into @AlterFieldName, @Length, @IsNullable, @AlterTableName
-- 創(chuàng)建主鍵
If (@AlterTableName <> @TmpTableName or @@fetch_status <> 0) and @PkFieldName <> ''
Begin
Set @PkFieldName = Left(@PkFieldName, Len(@PkFieldName) - 1)
Set @Sql = ' ALTER TABLE ' + @TmpTableName + ' ADD CONSTRAINT ' + @PkName
+ ' PRIMARY KEY CLUSTERED(' + @PkFieldName + ') ON [PRIMARY]'
Print @Sql
Exec(@Sql)
print '-----------------------------'
Set @PkFieldName = ''
End
End
Close curAlterInfo
Deallocate curAlterInfo
If @@Error > 0
Rollback Tran
Else
Commit Tran
Set NoCount Off