Page History: Schema Change Scripts - SQL Server

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Page Revision: Sat, Mar 02, 2013, 5:20 PM

Sequence of Statements¶

1. Drop foreign keys being created on existing tables
2. Drop tables being created
3. Drop code objects being created
4. Drop default constraints on columns being created
5. Drop columns being created
6. Drop/recreate schema
7. Create/alter tables ("alter" only includes adding columns)
8. Create primary keys
9. Create foreign keys
10. Populate lookup tables
11. Drop/recreate each code object in dependency order
    

Statement Syntax¶

1. Drop foreign keys being created on existing tables¶

if OBJECT_ID('SchemaName.FK_OnTable_AgainstTable') is not null alter table OnTable drop constraint [FK_OnTable_AgainstTable]

2. Drop tables being created¶

if object_id('SchemaName.TableName') is not null drop table SchemaName.TableName

3. Drop code objects being created¶

4. Drop Default Constraint on Columns Being Created¶

if exists (select * from sys.objects where name = 'DF_SchemaName_TableName_ColumnName')
    alter table SchemaName.TableName drop constraint DF_SchemaName_TableName_ColumnName

5. Drop Column¶

if COL_LENGTH('TableName','ColumnName') is not null
    alter table dbo.TableName drop column ColumnName

6. Drop/recreate schema¶

if exists (select 2 from sys.schemas where name = 'SchemaName') drop schema SchemaName
go    
create schema SchemaName authorization dbo
go

7. Create Tables and Add Columns¶

create table dbo.TableName (
     ColumnName  int         not null identity(1,1)
    ,ColumnName2 varchar(30) not null
    ,CONSTRAINT [PK_TableName] PRIMARY KEY CLUSTERED 
    ( [ColumnName] ASC ) WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, 
      ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

alter table dbo.TableName ADD
     ColumnName  int        not null identity(1,1)
    ,ColumnName2 date       not null
    ,ColumnName3 varchar(3) null     constraint DF_TableName_ColumnName3 DEFAULT 'XYZ' WITH VALUES

8. Create Primary Keys¶

This is necessary only if the CREATE TABLE script(s) didn't create them.

ALTER TABLE TableName ADD CONSTRAINT PK_TableName PRIMARY KEY CLUSTERED (TableNameID ASC) 
WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, 
ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]

9. Create foreign keys¶

ALTER TABLE OnSchema.OnTable WITH CHECK ADD CONSTRAINT [FK_OnTable_AgainstTable] 
FOREIGN KEY (OnColumn) REFERENCES AgainstSchema.AgainstTable (AgainstColumn)

Examples¶

Add a column

Note that there is NO COLUMN after ADD!

ALTER TABLE doc_exa ADD column_b VARCHAR(20) NULL

Add a non-nullable column with default values

ALTER TABLE MyTable ADD AddDate smalldatetime NOT NULL CONSTRAINT AddDateDflt DEFAULT getdate()

Add a nullable column with default values

ALTER TABLE MyTable ADD AddDate smalldatetime NULL CONSTRAINT AddDateDflt DEFAULT getdate() WITH VALUES

Drop a column

ALTER TABLE doc_exb DROP COLUMN column_b

Change a column

ALTER TABLE MyTable ALTER COLUMN NullCOl NVARCHAR(20) NOT NULL