SQL server convert int field to bit - sql

Question

I have a big database and I should to normalize it. One of the table contains field with type "integer" but it contains only 1 and 0 values. So it is good reason to convert this field to bit type. But when I try to save changes in SQL Server Management Studio it tells me that I can't do it. Also I have many field with values like nvarchar that should be converted to int or float that should be converted to int too.
Moreover I should create migration scripts for all changes so I can update real database without loosing data. Maybe somebody knows useful utility for this?
EDIT: It tells me that I can't update unable without drop it. And I want to update table without losing any data.
SQL version 2014

Answer 1

---Create one Temp. Column
Alter Table [dbo].[Demo2]
Add tempId int
GO
--Copy Data in temp. Coulmn
Update [dbo].[Demo2] set tempId=Id
--Drop column which you want to modify
Alter Table [dbo].[Demo2]
Drop Column Id
Go
--Create again that column with bit type
Alter Table [dbo].[Demo2]
Add Id bit
GO
--copy date back
Update [dbo].[Demo2] set Id=tempId
--drop temp column
Alter Table [dbo].[Demo2]
Drop Column tempId
Go

Answer 2

Here's how to add a new column to a table, set that column to the old column and then remove the old column
CREATE TABLE #test
(inttest int
)
Insert [#test]
( [inttest] )
Values ( 0
)
Insert [#test]
( [inttest] )
Values ( 1
)
Alter Table [#test] Add bittest bit
Update [#test] Set bittest=inttest
Alter Table [#test] Drop Column [inttest]
SELECT * FROM [#test] [T]

Answer 3

To generate migration script you don't need a special utility, SSMS does it pretty well.
Right-click the table in SSMS object explorer. Choose Design item in the context menu. Change the type of the column. In the main menu Table Designer choose item Generate Change Script. Save the generated script to a file, review it and make sure you understand each line in it before you run it on a production system. Adjust the script if needed.
On the other hand, to change the column type from int to bit you can use the ALTER TABLE statement:
ALTER TABLE dbo.TableName
ALTER COLUMN ColumnName bit NOT NULL
Before running this you should check that actual int values are indeed only 0 and 1.

Answer 4

After reading of all comments and posts I found solution in building procedure which will convert passed table and column in required. So I wrote this function
IF EXISTS (select * from dbo.sysobjects where id = object_id(N'IntToBit') and OBJECTPROPERTY(id, N'IsProcedure') = 1)
DROP PROCEDURE IntToBit
GO
IF OBJECT_ID('convertion_table', 'U') IS NOT NULL
DROP TABLE dbo.convertion_table;
go
CREATE TABLE dbo.convertion_table
(
bitTypeColumn bit NOT NULL DEFAULT 0,
intTypeColumnt integer ,
)
go
CREATE procedure IntToBit
#table nvarchar(150),
#column nvarchar(150)
AS
begin
DECLARE #sql nvarchar(4000)
SELECT #sql ='
--copy data to temp table
INSERT INTO convertion_table (bitTypeColumn)
SELECT '+#column +'
FROM ' +#table+'
--Drop column which you want to modify
Alter Table ' +#table+'
Drop Column '+#column +'
--Create again that column with bit type
Alter Table ' +#table+'
Add '+#column +' bit NOT NULL DEFAULT(0)
--copy date back
INSERT INTO '+#table+'('+#column+')
SELECT bitTypeColumn
FROM convertion_table
--cleare temp table
--DELETE bitTypeColumn FROM convertion_table
'
exec sp_executesql #sql
end
GO
and then call it passing field and table name :
exec dbo.IntToBit #table = 'tbl_SystemUsers', #column='intUseLogin';
Special thanks to Chris K and Hitesh Thakor

Answer 5

Simply Use TSql script to modify the table rather than using the designer
ALTER TABLE YourTableNameHere
ALTER COLUMN YourColumnNameHere INT
If you are using sql Server then you might wanna generate script for the table before altering the table so that you dont loose any data ..and you can simply retrieve everything using the script