SERIES: Modifying Tables Online
In the next few days I want to describe a way to modify the definition of very large tables while keeping the table available for other queries. Some table changes are already online operations. But offline changes need extra work to keep the table available. I explore one way to do that in this series.
This article used to be a single blog post, but I broke it into four parts because it seemed too long. Read Part 1, and understand the strategy I’m using. Treat Parts 2-4 as appendixes. When you want to use this plan (or one like it), come back and use them as examples. You won’t be able to make use of the examples by cutting and pasting directly (unless you happen to be running an bike equipment store called Adventureworks), but modifications shouldn’t be too hard.
- Part 1: Migration Strategy
- Part 2: Implementation Example
- Part 3: Same Example With Error Handling
- Part 4: Testing
- Part 5: Just One More Thing
This is part 3 of the series (you can consider this Appendix 2, The main article is found here).
What you find below is exactly the same script as you find in Part 2: Implementation Example with the exception that I’ve included error handling and wrappers to handle the following goals:
- If a statement fails, no data is lost
- If a statement fails, other queries are not impacted (i.e. we’re online)
- If a statement fails anywhere, it can be retried from the beginning with no lost work. This means for example that when data is copied to the staging table in batches, and that process is interrupted and restarted, the script “picks up where it left off”.
- The process is re-runnable. This means that if the script succeeds and for some reason the script is run again then no errors are raised and no work is performed.
- The last step, the switch, is an atomic transaction. It succeeds 100% or fails and rolls back 100%.
I present without any further comment, the scripts (with error-handling).
Create Staging Table
use AdventureWorks2012 -- original table isn't migrated, staging table doesn't exist IF NOT EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader_new' ) AND NOT EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader' AND COLUMN_NAME = 'Rowversion' ) BEGIN CREATE TABLE Sales.SalesOrderHeader_new( SalesOrderID int IDENTITY(1,1) NOT FOR REPLICATION NOT NULL, RevisionNumber tinyint NOT NULL, OrderDate datetime NOT NULL, DueDate datetime NOT NULL, ShipDate datetime NULL, [Status] tinyint NOT NULL, OnlineOrderFlag dbo.Flag NOT NULL, SalesOrderNumber AS (isnull(N'SO'+CONVERT(nvarchar(23),SalesOrderID),N'*** ERROR ***')), PurchaseOrderNumber dbo.OrderNumber NULL, AccountNumber dbo.AccountNumber NULL, CustomerID int NOT NULL, SalesPersonID int NULL, TerritoryID int NULL, BillToAddressID int NOT NULL, ShipToAddressID int NOT NULL, ShipMethodID int NOT NULL, CreditCardID int NULL, CreditCardApprovalCode varchar(15) NULL, CurrencyRateID int NULL, SubTotal money NOT NULL, TaxAmt money NOT NULL, Freight money NOT NULL, TotalDue AS (isnull((SubTotal+TaxAmt)+Freight,(0))), Comment nvarchar(128) NULL, rowguid uniqueidentifier ROWGUIDCOL NOT NULL, ModifiedDate datetime NOT NULL, [Rowversion] rowversion NOT NULL, -- This is the new column!! constraint PK_SalesOrderHeader_new_SalesOrderID primary key clustered (SalesOrderID ASC), constraint FK_SalesOrderHeader_new_Address_BillToAddressID foreign key(BillToAddressID) references Person.[Address] (AddressID), constraint FK_SalesOrderHeader_new_Address_ShipToAddressID foreign key(ShipToAddressID) references Person.[Address] (AddressID), constraint FK_SalesOrderHeader_new_CreditCard_CreditCardID foreign key(CreditCardID) references Sales.CreditCard (CreditCardID), constraint FK_SalesOrderHeader_new_CurrencyRate_CurrencyRateID foreign key(CurrencyRateID) references Sales.CurrencyRate (CurrencyRateID), constraint FK_SalesOrderHeader_new_Customer_CustomerID foreign key(CustomerID) references Sales.Customer (CustomerID), constraint FK_SalesOrderHeader_new_SalesPerson_SalesPersonID foreign key(SalesPersonID) references Sales.SalesPerson (BusinessEntityID), constraint FK_SalesOrderHeader_new_SalesTerritory_TerritoryID foreign key(TerritoryID) references Sales.SalesTerritory (TerritoryID), constraint FK_SalesOrderHeader_new_ShipMethod_ShipMethodID foreign key(ShipMethodID) references Purchasing.ShipMethod (ShipMethodID), constraint CK_SalesOrderHeader_new_DueDate check (DueDate>=OrderDate), constraint CK_SalesOrderHeader_new_Freight check (Freight>=0.00), constraint CK_SalesOrderHeader_new_ShipDate check (ShipDate>=OrderDate or ShipDate is null), constraint CK_SalesOrderHeader_new_Status check ([Status]>=0 and [Status]<=8), constraint CK_SalesOrderHeader_new_SubTotal check (SubTotal>=0.00), constraint CK_SalesOrderHeader_new_TaxAmt check (TaxAmt>=0.00) ) -- add default constraints alter table Sales.SalesOrderHeader_new add constraint DF_SalesOrderHeader_new_RevisionNumber default 0 for RevisionNumber, constraint DF_SalesOrderHeader_new_OrderDate default getdate() for OrderDate, constraint DF_SalesOrderHeader_new_Status default 1 for [Status], constraint DF_SalesOrderHeader_new_OnlineOrderFlag default 1 for OnlineOrderFlag, constraint DF_SalesOrderHeader_new_SubTotal default 0.00 for SubTotal, constraint DF_SalesOrderHeader_new_TaxAmt default 0.00 for TaxAmt, constraint DF_SalesOrderHeader_new_Freight default 0.00 for Freight, constraint DF_SalesOrderHeader_new_rowguid default newid() for rowguid, constraint DF_SalesOrderHeader_new_ModifiedDate default getdate() for ModifiedDate -- two nc ak create unique nonclustered index AK_SalesOrderHeader_new_rowguid on Sales.SalesOrderHeader_new(rowguid ASC) create unique nonclustered index AK_SalesOrderHeader_new_SalesOrderNumber on Sales.SalesOrderHeader_new(SalesOrderNumber) -- two nc ix create nonclustered index IX_SalesOrderHeader_new_CustomerID on Sales.SalesOrderHeader_new(CustomerID) create nonclustered index IX_SalesOrderHeader_new_SalesPersonID on Sales.SalesOrderHeader_new(SalesPersonID) END GO |
Add Triggers
-- staging table exists -- original table isn't migrated, -- triggers don't exist IF EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader_new' ) AND NOT EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader' AND COLUMN_NAME = 'Rowversion' ) AND NOT EXISTS ( SELECT 1 FROM sys.triggers WHERE name = 't_i_SalesOrderHeader' ) BEGIN EXEC sp_executesql N' create trigger t_i_SalesOrderHeader on Sales.SalesOrderHeader after insert as set identity_insert Sales.SalesOrderHeader_new on; insert SalesOrderHeader_new(SalesOrderID, RevisionNumber, OrderDate, DueDate, ShipDate, [Status], OnlineOrderFlag, PurchaseOrderNumber, AccountNumber, CustomerID, SalesPersonID, TerritoryID, BillToAddressID, ShipToAddressID, ShipMethodID, CreditCardID, CreditCardApprovalCode, CurrencyRateID, SubTotal, TaxAmt, Freight, Comment, rowguid, ModifiedDate) select SalesOrderID, RevisionNumber, OrderDate, DueDate, ShipDate, [Status], OnlineOrderFlag, PurchaseOrderNumber, AccountNumber, CustomerID, SalesPersonID, TerritoryID, BillToAddressID, ShipToAddressID, ShipMethodID, CreditCardID, CreditCardApprovalCode, CurrencyRateID, SubTotal, TaxAmt, Freight, Comment, rowguid, ModifiedDate from inserted set identity_insert Sales.SalesOrderHeader_new off;'; END GO IF EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader_new' ) AND NOT EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader' AND COLUMN_NAME = 'Rowversion' ) AND NOT EXISTS ( SELECT 1 FROM sys.triggers WHERE name = 't_u_SalesOrderHeader' ) BEGIN EXEC sp_executesql N' create trigger t_u_SalesOrderHeader on Sales.SalesOrderHeader after update as -- assuming pk values are never altered. update Sales.SalesOrderHeader_new set RevisionNumber = i.RevisionNumber, OrderDate = i.OrderDate, DueDate = i.DueDate, ShipDate = i.ShipDate, [Status] = i.[Status], OnlineOrderFlag = i.OnlineOrderFlag, PurchaseOrderNumber = i.PurchaseOrderNumber, AccountNumber = i.AccountNumber, CustomerID = i.CustomerID, SalesPersonID = i.SalesPersonID, TerritoryID = i.TerritoryID, BillToAddressID = i.BillToAddressID, ShipToAddressID = i.ShipToAddressID, ShipMethodID = i.ShipMethodID, CreditCardID = i.CreditCardID, CreditCardApprovalCode = i.CreditCardApprovalCode, CurrencyRateID = i.CurrencyRateID, SubTotal = i.SubTotal, TaxAmt = i.TaxAmt, Freight = i.Freight, Comment = i.Comment, rowguid = i.rowguid, ModifiedDate = i.ModifiedDate from Sales.SalesOrderHeader_new s join inserted i on s.SalesOrderID = i.SalesOrderID;'; END GO IF EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader_new' ) AND NOT EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader' AND COLUMN_NAME = 'Rowversion' ) AND NOT EXISTS ( SELECT 1 FROM sys.triggers WHERE name = 't_d_SalesOrderHeader' ) BEGIN EXEC sp_executesql N' create trigger t_d_SalesOrderHeader on Sales.SalesOrderHeader after delete as delete Sales.SalesOrderHeader_new from Sales.SalesOrderHeader_new s join deleted d on d.SalesOrderID = s.SalesOrderID ;'; END GO |
Move the data over in batches
set nocount on; set transaction isolation level serializable; set deadlock_priority LOW declare @i int; declare @new_i int = 0; declare @largestSalesOrderId int; declare @minBatchSize int = 5000 set identity_insert Sales.SalesOrderHeader_new on; -- largest SalesOrderId to migrate select @largestSalesOrderId = isnull(max(SalesOrderID), 0) from Sales.SalesOrderHeader -- get @i to be just under the lowest SalesOrderId to migrate select top 1 @i = so.SalesOrderId - 1 from Sales.SalesOrderHeader so left join Sales.SalesOrderHeader_new so_new ON so.SalesOrderId = so_new.SalesOrderId where so_new.SalesOrderId is null ORDER BY so.SalesOrderId -- batch loop while @i < @largestSalesOrderId begin declare @counter int = 0; declare @error int = 0; -- retry loop: while (1=1) begin begin try select top (@minBatchSize) @new_i = SalesOrderID from Sales.SalesOrderHeader where SalesOrderID > @i order by SalesOrderID asc; merge Sales.SalesOrderHeader_new as target using ( select SalesOrderID, RevisionNumber, OrderDate, DueDate, ShipDate, [Status], OnlineOrderFlag, PurchaseOrderNumber, AccountNumber, CustomerID, SalesPersonID, TerritoryID, BillToAddressID, ShipToAddressID, ShipMethodID, CreditCardID, CreditCardApprovalCode, CurrencyRateID, SubTotal, TaxAmt, Freight, Comment, rowguid, ModifiedDate from Sales.SalesOrderHeader where SalesOrderID > @i and SalesOrderID <= @new_i ) as source (SalesOrderID, RevisionNumber, OrderDate, DueDate, ShipDate, [Status], OnlineOrderFlag, PurchaseOrderNumber, AccountNumber, CustomerID, SalesPersonID, TerritoryID, BillToAddressID, ShipToAddressID, ShipMethodID, CreditCardID, CreditCardApprovalCode, CurrencyRateID, SubTotal, TaxAmt, Freight, Comment, rowguid, ModifiedDate) on target.SalesOrderID = source.SalesOrderID when not matched then insert (SalesOrderID, RevisionNumber, OrderDate, DueDate, ShipDate, [Status], OnlineOrderFlag, PurchaseOrderNumber, AccountNumber, CustomerID, SalesPersonID, TerritoryID, BillToAddressID, ShipToAddressID, ShipMethodID, CreditCardID, CreditCardApprovalCode, CurrencyRateID, SubTotal, TaxAmt, Freight, Comment, rowguid, ModifiedDate) values (source.SalesOrderID, source.RevisionNumber, source.OrderDate, source.DueDate, source.ShipDate, source.[Status], source.OnlineOrderFlag, source.PurchaseOrderNumber, source.AccountNumber, source.CustomerID, source.SalesPersonID, source.TerritoryID, source.BillToAddressID, source.ShipToAddressID, source.ShipMethodID, source.CreditCardID, source.CreditCardApprovalCode, source.CurrencyRateID, source.SubTotal, source.TaxAmt, source.Freight, source.Comment, source.rowguid, source.ModifiedDate); --success select @i = @new_i, @error = 0; break; end try begin catch select @counter = @counter + 1, @error = @@ERROR; if (@counter >= 5) begin -- this batch failed five times! Something's wrong raiserror (N'Could not copy Sales.SalesOrderHeader rows to Sales.SalesOrderHeader_new', 16, 1, @error); break; end end catch end if @error <> 0 begin -- an error has been raised. Discontinue. break; end end set identity_insert Sales.SalesOrderHeader_new off; go |
Do The Switch
set xact_abort on set deadlock_priority high set transaction isolation level serializable begin transaction IF EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = 'Sales' AND TABLE_NAME = 'SalesOrderHeader_new' ) BEGIN begin try -- rename pks and indexes from original table exec sp_rename N'Sales.PK_SalesOrderHeader_SalesOrderID', N'PK_SalesOrderHeader_old_SalesOrderID', N'OBJECT'; exec sp_rename N'Sales.SalesOrderHeader.AK_SalesOrderHeader_rowguid', N'AK_SalesOrderHeader_old_rowguid', N'INDEX' exec sp_rename N'Sales.SalesOrderHeader.AK_SalesOrderHeader_SalesOrderNumber', N'AK_SalesOrderHeader_old_SalesOrderNumber', N'INDEX' exec sp_rename N'Sales.SalesOrderHeader.IX_SalesOrderHeader_CustomerID', N'IX_SalesOrderHeader_old_CustomerID', N'INDEX' exec sp_rename N'Sales.SalesOrderHeader.IX_SalesOrderHeader_SalesPersonID', N'IX_SalesOrderHeader_old_SalesPersonID', N'INDEX' -- rename checks and defaults exec sp_rename N'Sales.CK_SalesOrderHeader_Status', 'CK_SalesOrderHeader_old_Status', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_DueDate', 'CK_SalesOrderHeader_old_DueDate', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_ShipDate', 'CK_SalesOrderHeader_old_ShipDate', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_SubTotal', 'CK_SalesOrderHeader_old_SubTotal', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_TaxAmt', 'CK_SalesOrderHeader_old_TaxAmt', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_Freight', 'CK_SalesOrderHeader_old_Freight', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_RevisionNumber', 'DF_SalesOrderHeader_old_RevisionNumber', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_OrderDate', 'DF_SalesOrderHeader_old_OrderDate', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_Status', 'DF_SalesOrderHeader_old_Status', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_OnlineOrderFlag', 'DF_SalesOrderHeader_old_OnlineOrderFlag', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_SubTotal', 'DF_SalesOrderHeader_old_SubTotal', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_TaxAmt', 'DF_SalesOrderHeader_old_TaxAmt', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_Freight', 'DF_SalesOrderHeader_old_Freight', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_rowguid', 'DF_SalesOrderHeader_old_rowguid', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_ModifiedDate', 'DF_SalesOrderHeader_old_ModifiedDate', N'OBJECT'; -- drop fks from original table alter table Sales.SalesOrderHeader drop constraint FK_SalesOrderHeader_Address_BillToAddressID, FK_SalesOrderHeader_Address_ShipToAddressID, FK_SalesOrderHeader_CreditCard_CreditCardID, FK_SalesOrderHeader_CurrencyRate_CurrencyRateID, FK_SalesOrderHeader_Customer_CustomerID, FK_SalesOrderHeader_SalesPerson_SalesPersonID, FK_SalesOrderHeader_ShipMethod_ShipMethodID, FK_SalesOrderHeader_SalesTerritory_TerritoryID -- drop fks to original table alter table Sales.SalesOrderDetail drop constraint FK_SalesOrderDetail_SalesOrderHeader_SalesOrderID; alter table Sales.SalesOrderHeaderSalesReason drop constraint FK_SalesOrderHeaderSalesReason_SalesOrderHeader_SalesOrderID; -- drop triggers on original table drop trigger Sales.t_i_SalesOrderHeader; drop trigger Sales.t_u_SalesOrderHeader; drop trigger Sales.t_d_SalesOrderHeader; -- drop uSalesOrderHeader (but remember its definition) declare @triggersql nvarchar(max); select @triggersql = OBJECT_DEFINITION(object_id) from sys.triggers where name = 'uSalesOrderHeader'; drop trigger Sales.uSalesOrderHeader; -- rename original table to "old" exec sp_rename N'Sales.SalesOrderHeader', N'SalesOrderHeader_old', N'OBJECT'; --rename the new indexes exec sp_rename N'Sales.PK_SalesOrderHeader_new_SalesOrderID', N'PK_SalesOrderHeader_SalesOrderID', N'OBJECT'; exec sp_rename N'Sales.SalesOrderHeader_new.AK_SalesOrderHeader_new_rowguid', N'AK_SalesOrderHeader_rowguid', N'INDEX' exec sp_rename N'Sales.SalesOrderHeader_new.AK_SalesOrderHeader_new_SalesOrderNumber', N'AK_SalesOrderHeader_SalesOrderNumber', N'INDEX' exec sp_rename N'Sales.SalesOrderHeader_new.IX_SalesOrderHeader_new_CustomerID', N'IX_SalesOrderHeader_CustomerID', N'INDEX' exec sp_rename N'Sales.SalesOrderHeader_new.IX_SalesOrderHeader_new_SalesPersonID', N'IX_SalesOrderHeader_SalesPersonID', N'INDEX' -- rename the new checks and defaults exec sp_rename N'Sales.CK_SalesOrderHeader_new_Status', 'CK_SalesOrderHeader_Status', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_new_DueDate', 'CK_SalesOrderHeader_DueDate', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_new_ShipDate', 'CK_SalesOrderHeader_ShipDate', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_new_SubTotal', 'CK_SalesOrderHeader_SubTotal', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_new_TaxAmt', 'CK_SalesOrderHeader_TaxAmt', N'OBJECT'; exec sp_rename N'Sales.CK_SalesOrderHeader_new_Freight', 'CK_SalesOrderHeader_Freight', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_RevisionNumber', 'DF_SalesOrderHeader_RevisionNumber', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_OrderDate', 'DF_SalesOrderHeader_OrderDate', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_Status', 'DF_SalesOrderHeader_Status', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_OnlineOrderFlag', 'DF_SalesOrderHeader_OnlineOrderFlag', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_SubTotal', 'DF_SalesOrderHeader_SubTotal', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_TaxAmt', 'DF_SalesOrderHeader_TaxAmt', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_Freight', 'DF_SalesOrderHeader_Freight', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_rowguid', 'DF_SalesOrderHeader_rowguid', N'OBJECT'; exec sp_rename N'Sales.DF_SalesOrderHeader_new_ModifiedDate', 'DF_SalesOrderHeader_ModifiedDate', N'OBJECT'; -- rename "new" table exec sp_rename N'Sales.SalesOrderHeader_new', N'SalesOrderHeader', N'OBJECT'; --rename fks pointing out exec sp_rename N'Sales.FK_SalesOrderHeader_new_Address_BillToAddressID', N'FK_SalesOrderHeader_Address_BillToAddressID', N'OBJECT' exec sp_rename N'Sales.FK_SalesOrderHeader_new_Address_ShipToAddressID', N'FK_SalesOrderHeader_Address_ShipToAddressID', N'OBJECT' exec sp_rename N'Sales.FK_SalesOrderHeader_new_CreditCard_CreditCardID', N'FK_SalesOrderHeader_CreditCard_CreditCardID', N'OBJECT' exec sp_rename N'Sales.FK_SalesOrderHeader_new_CurrencyRate_CurrencyRateID', N'FK_SalesOrderHeader_CurrencyRate_CurrencyRateID', N'OBJECT' exec sp_rename N'Sales.FK_SalesOrderHeader_new_Customer_CustomerID', N'FK_SalesOrderHeader_Customer_CustomerID', N'OBJECT' exec sp_rename N'Sales.FK_SalesOrderHeader_new_SalesPerson_SalesPersonID', N'FK_SalesOrderHeader_SalesPerson_SalesPersonID', N'OBJECT' exec sp_rename N'Sales.FK_SalesOrderHeader_new_ShipMethod_ShipMethodID', N'FK_SalesOrderHeader_ShipMethod_ShipMethodID', N'OBJECT' exec sp_rename N'Sales.FK_SalesOrderHeader_new_SalesTerritory_TerritoryID', N'FK_SalesOrderHeader_SalesTerritory_TerritoryID', N'OBJECT' -- re-add fks pointing in (without checks for now) alter table Sales.SalesOrderDetail with nocheck add constraint FK_SalesOrderDetail_SalesOrderHeader_SalesOrderID foreign key (SalesOrderId) references Sales.SalesOrderHeader(SalesOrderId) alter table Sales.SalesOrderHeaderSalesReason with nocheck add constraint FK_SalesOrderHeaderSalesReason_SalesOrderHeader_SalesOrderID foreign key (SalesOrderId) references Sales.SalesOrderHeader(SalesOrderId) -- re-add trigger (use sp_executesql in order to keep in transaction) exec sp_executesql @triggersql; end try begin catch declare @error nvarchar(max) = ERROR_MESSAGE(); select 'An error was encountered... Rolling back' as [message], @error as errorMessage raiserror (@error, 16, 1) rollback end catch END if @@TRANCOUNT > 0 commit GO |
Great writeup!
One question/suggestion, have you considered using a new schema (e.g. Sales_New) and creating the new table in that schema? The benefit is that all the defaults, keys, triggers, and indexes can retain the same names as the original, and the switch becomes a single ALTER SCHEMA…TRANSFER operation. (or two, one for the old table and one for the new)
Comment by Rob Volk — April 24, 2012 @ 7:21 am
Excellent comment Rob! In fact I did think of using a new schema. But I thought of it too late and the article was already published. It’s definitely the simpler way to go (and simpler is better).
Maybe I’ll add an extra part onto this series explaining that strategy.
Comment by Michael J. Swart — April 24, 2012 @ 7:40 am
[…] Modifying Tables Online – Part 3: Example With Error Handling – Here’s Part 3 of this excellent series from Michael J. Swart (Blog|Twitter). […]
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