Если вы вносите изменения в Management Studio и генерируете сценарии, она создает новую таблицу и вставляет в нее старые данные с измененными типами данных. Вот небольшой пример изменения двух типов данных столбца
/*
12 August 201008:30:39
User:
Server: CLPPRGRTEL01\TELSQLEXPRESS
Database: Tracker_3
Application:
*/
/* To prevent any potential data loss issues, you should review this script in detail before running it outside the context of the database designer.*/
BEGIN TRANSACTION
SET QUOTED_IDENTIFIER ON
SET ARITHABORT ON
SET NUMERIC_ROUNDABORT OFF
SET CONCAT_NULL_YIELDS_NULL ON
SET ANSI_NULLS ON
SET ANSI_PADDING ON
SET ANSI_WARNINGS ON
COMMIT
BEGIN TRANSACTION
GO
ALTER TABLE dbo.tblDiary
DROP CONSTRAINT FK_tblDiary_tblDiary_events
GO
ALTER TABLE dbo.tblDiary_events SET (LOCK_ESCALATION = TABLE)
GO
COMMIT
BEGIN TRANSACTION
GO
CREATE TABLE dbo.Tmp_tblDiary
(
Diary_ID int NOT NULL IDENTITY (1, 1),
Date date NOT NULL,
Diary_event_type_ID int NOT NULL,
Notes varchar(MAX) NULL,
Expected_call_volumes real NULL,
Expected_duration real NULL,
Skill_affected smallint NULL
) ON T3_Data_2
TEXTIMAGE_ON T3_Data_2
GO
ALTER TABLE dbo.Tmp_tblDiary SET (LOCK_ESCALATION = TABLE)
GO
SET IDENTITY_INSERT dbo.Tmp_tblDiary ON
GO
IF EXISTS(SELECT * FROM dbo.tblDiary)
EXEC('INSERT INTO dbo.Tmp_tblDiary (Diary_ID, Date, Diary_event_type_ID, Notes, Expected_call_volumes, Expected_duration, Skill_affected)
SELECT Diary_ID, Date, Diary_event_type_ID, CONVERT(varchar(MAX), Notes), Expected_call_volumes, Expected_duration, CONVERT(smallint, Skill_affected) FROM dbo.tblDiary WITH (HOLDLOCK TABLOCKX)')
GO
SET IDENTITY_INSERT dbo.Tmp_tblDiary OFF
GO
DROP TABLE dbo.tblDiary
GO
EXECUTE sp_rename N'dbo.Tmp_tblDiary', N'tblDiary', 'OBJECT'
GO
ALTER TABLE dbo.tblDiary ADD CONSTRAINT
PK_tblDiary PRIMARY KEY NONCLUSTERED
(
Diary_ID
) WITH( PAD_INDEX = OFF, FILLFACTOR = 86, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON T3_Data_2
GO
CREATE UNIQUE CLUSTERED INDEX tblDiary_ID ON dbo.tblDiary
(
Diary_ID
) WITH( PAD_INDEX = OFF, FILLFACTOR = 86, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON T3_Data_2
GO
CREATE NONCLUSTERED INDEX tblDiary_date ON dbo.tblDiary
(
Date
) WITH( PAD_INDEX = OFF, FILLFACTOR = 86, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON T3_Data_2
GO
ALTER TABLE dbo.tblDiary WITH NOCHECK ADD CONSTRAINT
FK_tblDiary_tblDiary_events FOREIGN KEY
(
Diary_event_type_ID
) REFERENCES dbo.tblDiary_events
(
Diary_event_ID
) ON UPDATE CASCADE
ON DELETE CASCADE
GO
COMMIT