The script that is generated won't run by default because of the duplicate declaration of @var0 without a GO inserted between the batches.
DECLARE @var0 nvarchar(128)
SELECT @var0 = name
FROM sys.default_constraints
WHERE parent_object_id = object_id(N'__MigrationHistory')
AND col_name(parent_object_id, parent_column_id) = 'CreatedOn';
IF @var0 IS NOT NULL
EXECUTE('ALTER TABLE [__MigrationHistory] DROP CONSTRAINT ' + @var0)
ALTER TABLE [__MigrationHistory] DROP COLUMN [CreatedOn]
DECLARE @var0 nvarchar(128)
SELECT @var0 = name
FROM sys.default_constraints
WHERE parent_object_id = object_id(N'dbo.Customer')
AND col_name(parent_object_id, parent_column_id) = 'EmailAddress';
IF @var0 IS NOT NULL
EXECUTE('ALTER TABLE [dbo].[Customer] DROP CONSTRAINT ' + @var0)
ALTER TABLE [dbo].[Customer] DROP COLUMN [EmailAddress]
INSERT INTO [__MigrationHistory] ([MigrationId], [Model], [ProductVersion]) VALUES ('201206100637386_AutomaticMigration', 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rc.net40')
DECLARE @var0 nvarchar(128)
SELECT @var0 = name
FROM sys.default_constraints
WHERE parent_object_id = object_id(N'__MigrationHistory')
AND col_name(parent_object_id, parent_column_id) = 'CreatedOn';
IF @var0 IS NOT NULL
EXECUTE('ALTER TABLE [__MigrationHistory] DROP CONSTRAINT ' + @var0)
ALTER TABLE [__MigrationHistory] DROP COLUMN [CreatedOn]
DECLARE @var0 nvarchar(128)
SELECT @var0 = name
FROM sys.default_constraints
WHERE parent_object_id = object_id(N'dbo.Customer')
AND col_name(parent_object_id, parent_column_id) = 'EmailAddress';
IF @var0 IS NOT NULL
EXECUTE('ALTER TABLE [dbo].[Customer] DROP CONSTRAINT ' + @var0)
ALTER TABLE [dbo].[Customer] DROP COLUMN [EmailAddress]
INSERT INTO [__MigrationHistory] ([MigrationId], [Model], [ProductVersion]) VALUES ('201206100637386_AutomaticMigration', 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rc.net40')