Run a migration script where a column is created and then updated - sql-server

Question

I have this script where I want to add a SurveyId and remove a ContractId from the SOR table.
However the script will not run because the SurveyId is created in the script and is considered to be an invalid column as it does not exist before it is created.
So how do I fix this?
See
-- Start of script
PRINT 'Start of script'
IF NOT EXISTS ( SELECT 1
FROM information_schema.COLUMNS
WHERE table_schema = 'dbo'
AND TABLE_NAME = 'Sor'
AND column_Name = 'ContractId' )
BEGIN
PRINT 'The colmun ContractId does not exist in Sor table'
GOTO EndScript
END
BEGIN TRANSACTION
GO
IF ##ERROR <> 0
BEGIN
GOTO ErrorScript
END
PRINT 'Begin Transaction'
-- Add the new SurveyId field to both Questions and SOR
IF EXISTS ( SELECT 1
FROM information_schema.COLUMNS
WHERE table_schema = 'dbo'
AND TABLE_NAME = 'Sor'
AND column_Name = 'SurveyId' )
BEGIN
PRINT 'The colmun SurveyId already exists in Sor table'
GOTO RemoveUnwantedData
END
ALTER TABLE [dbo].[Sor]
ADD SurveyId int null
IF ##ERROR <> 0
BEGIN
PRINT 'Error: ' + CAST(##ERROR AS VARCHAR(10)) + '. Failed to add SurveyId column to the Sor table.'
GOTO ErrorScript
END
PRINT 'SurveyId column successfully added to the Sor table'
RemoveUnwantedData:
-- Remove ContractId = 0 - invalid rows
DELETE FROM [dbo].[Sor]
WHERE ContractId = 0
IF ##ERROR <> 0
BEGIN
PRINT 'Error: ' + CAST(##ERROR AS VARCHAR(10)) + '. Failed to delete ContractId = 0 in the Sor table.'
GOTO ErrorScript
END
PRINT 'Removed rows in Sor where ContractId = 0, if there are any'
-- Create a query to populate the SurveyId
UPDATE [dbo].[Sor]
SET SurveyId = vw.SurveyId -- **<----ERROR HERE!!!!!!!! --**
FROM dbo.FirstSurveyIdForContractId vw WHERE vw.ContractId = dbo.Sor.ContractId
IF ##ERROR <> 0
BEGIN
PRINT 'Error: ' + CAST(##ERROR AS VARCHAR(10)) + '. Failed to populate SurveyId in the Sor table.'
GOTO ErrorScript
END
PRINT 'SurveyIds successfully populated in the Sor table'
-- Check if SurveyId can be made not null
DECLARE #NumberOfNullEntriesSors INT
SELECT #NumberOfNullEntriesSors = COUNT(*) FROM [dbo].[Sor] WHERE SurveyId IS NULL
IF #NumberOfNullEntriesSors > 0
BEGIN
PRINT 'There are ' + CAST(#NumberOfNullEntriesSors as VARCHAR(10)) + ' SurveyIds for SORs not set, check the data before proceeding'
GOTO EndScript
END
PRINT 'All SurveyIds set and now SurveyId can be made not null.'
-- Alter SurveyId to not null
ALTER TABLE [dbo].[Sor]
ALTER COLUMN SurveyId int NOT NULL
IF ##ERROR <> 0
BEGIN
PRINT 'Error: ' + CAST(##ERROR AS VARCHAR(10)) + ' Failed to set SurveyId for Sor table to not null'
GOTO ErrorScript
END
PRINT 'SurveyId now not null'
-- Create new foreign key relationships for SurveyId
ALTER TABLE [dbo].[Sor] ADD CONSTRAINT [FK_Sor_Survey]
FOREIGN KEY ([SurveyId]) REFERENCES [dbo].[Survey] ([ID])
IF ##ERROR <> 0
BEGIN
PRINT 'Error: ' + CAST(##ERROR AS VARCHAR(10)) + ' Failed to set foreign key SurveyId for Sor table.'
GOTO ErrorScript
END
PRINT 'Foreign key relationships set for Sor tables on SurveyId'
-- Remove the ContractId column
ALTER TABLE [dbo].[Sor]
DROP COLUMN ContractId
IF ##ERROR <> 0
BEGIN
PRINT 'Error: ' + CAST(##ERROR AS VARCHAR(10)) + ' Failed to drop ContractId column from Sor table.'
GOTO ErrorScript
END
PRINT 'ContractId column dropped from SOR tables'
GOTO SuccessScript
ErrorScript:
PRINT 'ErrorScript Started'
ROLLBACK TRANSACTION
PRINT 'ErrorScript Completed'
GOTO Endscript
SuccessScript:
Print 'SuccessScript Started'
COMMIT TRANSACTION
PRINT 'SuccessScript Completed'
EndScript:
Print 'End of Script'

Answer 1

Use GO after the ALTER TABLE statement and before the UPDATE statement.
Signals the end of a batch of Transact-SQL statements to the SQL
Server utilities.
Also, because a transaction cannot span more than 1 batch, you need to break your transaction up into 2 transactions. An alternative to using GOTO for error handling in this situation is to use TRY/CATCH for each transaction as follows:
-- first batch
BEGIN TRANSACTION;
BEGIN TRY
...
ALTER TABLE [dbo].[Sor]
ADD SurveyId int null
...
END TRY
BEGIN CATCH
IF ##TRANCOUNT > 0
ROLLBACK TRANSACTION;
END CATCH;
IF ##TRANCOUNT > 0
COMMIT TRANSACTION;
GO
-- second batch
BEGIN TRANSACTION;
BEGIN TRY
...
UPDATE [dbo].[Sor]
SET SurveyId = vw.SurveyId -- **<----ERROR HERE!!!!!!!! --**
FROM dbo.FirstSurveyIdForContractId vw WHERE vw.ContractId = dbo.Sor.ContractId
...
END TRY
BEGIN CATCH
IF ##TRANCOUNT > 0
ROLLBACK TRANSACTION;
END CATCH;
IF ##TRANCOUNT > 0
COMMIT TRANSACTION;
GO