I have been having difficulty migrating a U8 Site to U9 and originally posted about it on the Umbraco Facebook group(link below)

https://www.facebook.com/photo?fbid=10227095786723405&set=gm.1479985932403293

As it turns out, there were orphaned records in the db that seem to have been the cause. My fix was to write a SQL Script that migrates the data from a U8 database to a Clean U9. I am including it below for anyone else that may benefit.

I am still in the process of migrating the site. My problem is I am getting this error on the back end when I click on a page in the Content Tree:

Request error: The URL returned a 404 (not found): /umbraco/backoffice/umbracoapi/content/GetById

Any Ideas?

Thanks!

SQL SERVER MIGRATION SCRIPT

=============================================    
-- Author:  Graham Davis    
-- Company: zBestData.com    
-- Created: 02/18/2022    
-- Updated: 02/18/2022 - Initial Script    
--              
-- Description: Convert Umbraco 8 Database to Umbraco 9     
--              using a clean U9 MDF    
-- =============================================

SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoNode] ON;
INSERT INTO[Umbraco9].[dbo].[umbracoNode] ([id]
      ,[uniqueId]
      ,[parentId]
      ,[level]
      ,[path]
      ,[sortOrder]
      ,[trashed]
      ,[nodeUser]
      ,[text]
      ,[nodeObjectType]
      ,[createDate])

SELECT * FROM [Umbraco8].[dbo].[umbracoNode]
WHERE id NOT IN (SELECT id FROM [Umbraco9].[dbo].[umbracoNode]); 
SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoNode] OFF;

SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsContentType] ON;
INSERT INTO[Umbraco9].[dbo].[cmsContentType] ([pk]
      ,[nodeId]
      ,[alias]
      ,[icon]
      ,[thumbnail]
      ,[description]
      ,[isContainer]
      ,[isElement]
      ,[allowAtRoot]
      ,[variations])

SELECT * FROM [Umbraco8].[dbo].[cmsContentType] 
WHERE pk NOT IN (SELECT pk FROM [Umbraco9].[dbo].[cmsContentType])
SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsContentType] OFF;

INSERT INTO[Umbraco9].[dbo].[umbracoContent]( [nodeId]
      ,[contentTypeId])
SELECT * FROM [Umbraco8].[dbo].[umbracoContent]
WHERE contentTypeId IN (SELECT nodeId FROM [Umbraco9].[dbo].[cmsContentType]);

INSERT INTO[Umbraco9].[dbo].[cmsContentNu] ([nodeId]
      ,[published]
      ,[data]
      ,[rv])
SELECT * FROM [Umbraco8].[dbo].[cmsContentNu]
WHERE nodeId  IN (SELECT nodeId FROM [Umbraco9].[dbo].[umbracoContent]);

INSERT INTO[Umbraco9].[dbo].[cmsContentType2ContentType] ([parentContentTypeId]
      ,[childContentTypeId])
SELECT * FROM [Umbraco8].[dbo].[cmsContentType2ContentType];

INSERT INTO[Umbraco9].[dbo].[cmsContentType2ContentType] ([parentContentTypeId]
      ,[childContentTypeId])
 SELECT * FROM [Umbraco8].[dbo].[cmsContentType2ContentType]
 WHERE parentContentTypeId NOT IN (SELECT parentContentTypeId FROM [Umbraco9].[dbo].[cmsContentType2ContentType]);

 SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsTemplate] ON;
INSERT INTO[Umbraco9].[dbo].[cmsTemplate]([pk]
      ,[nodeId]
      ,[alias])
 SELECT * FROM [Umbraco8].[dbo].[cmsTemplate]
 SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsTemplate] OFF;


 INSERT INTO[Umbraco9].[dbo].[cmsDocumentType] ([contentTypeNodeId]
      ,[templateNodeId]
      ,[IsDefault])  
SELECT * FROM [Umbraco8].[dbo].[cmsDocumentType]
WHERE [contentTypeNodeId]  IN (
SELECT nodeId FROM [Umbraco9].[dbo].cmsContentType)

INSERT INTO[Umbraco9].[dbo].[umbracoDocument] ( [nodeId]
      ,[published]
      ,[edited])
SELECT * FROM [Umbraco8].[dbo].[umbracoDocument]
WHERE nodeId IN ( SELECT nodeId FROM [Umbraco9].[dbo].[umbracoContent])

 SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoContentVersion] ON;
INSERT INTO[Umbraco9].[dbo].[umbracoContentVersion] ([id]
      ,[nodeId]
      ,[versionDate]
      ,[userId]
      ,[current]
      ,[text])
      --,[preventCleanup])
      SELECT [id]
      ,[nodeId]
      ,[versionDate]
      ,[userId]
      ,[current]
      ,[text]
FROM [Umbraco8].[dbo].[umbracoContentVersion] WHERE [current] = 1 
AND nodeId IN ( SELECT nodeId FROM [Umbraco9].[dbo].[umbracoContent])
SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoContentVersion] OFF;

INSERT INTO[Umbraco9].[dbo].[umbracoContentSchedule]( [id]
      ,[nodeId]
      ,[languageId]
      ,[date]
      ,[action])
SELECT * FROM [Umbraco8].[dbo].[umbracoContentSchedule];


INSERT INTO[Umbraco9].[dbo].[umbracoDataType] ([nodeId]
      ,[propertyEditorAlias]
      ,[dbType]
      ,[config])
  SELECT * FROM [Umbraco8].[dbo].[umbracoDataType]
  WHERE nodeId NOT IN (SELECT nodeId FROM [Umbraco9].[dbo].[umbracoDataType]);

INSERT INTO[Umbraco9].[dbo].[umbracoDocumentVersion] ([id]
    ,[templateId]
    ,[published])
SELECT * FROM [Umbraco8].[dbo].[umbracoDocumentVersion] WHERE published = 1
AND id IN (SELECT id FROM [umbracoContentVersion]);

INSERT INTO[Umbraco9].[dbo].[umbracoMediaVersion] ([id]
      ,[paath])
  SELECT * FROM [Umbraco8].[dbo].[umbracoMediaVersion]

SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsPropertyTypeGroup] ON;
INSERT INTO[Umbraco9].[dbo].[cmsPropertyTypeGroup] (id
      ,[uniqueID]
      ,[contenttypeNodeId]
      --,[type]
      ,[text]
      ,[alias]
      ,[sortorder])

SELECT id
      ,[uniqueID]
      ,[contenttypeNodeId]
      --,[type]
      ,[text]
      ,[text] AS [alias]
      ,[sortorder]

FROM [Umbraco8].[dbo].[cmsPropertyTypeGroup]
WHERE id NOT IN (SELECT id FROM [Umbraco9].[dbo].[cmsPropertyTypeGroup]);
SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsPropertyTypeGroup] OFF;

SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsPropertyType] ON;
INSERT INTO[Umbraco9].[dbo].[cmsPropertyType] ([id]
      ,[dataTypeId]
      ,[contentTypeId]
      ,[propertyTypeGroupId]
      ,[Alias]
      ,[Name]
      ,[sortOrder]
      ,[mandatory]
      ,[mandatoryMessage]
      ,[validationRegExp]
      ,[validationRegExpMessage]
      ,[Description]
      ,[labelOnTop]
      ,[variations]
      ,[UniqueID])

SELECT * FROM [Umbraco8].[dbo].[cmsPropertyType] 
WHERE id NOT IN (SELECT id FROM [Umbraco9].[dbo].[cmsPropertyType]);
SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsPropertyType] OFF;

SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoPropertyData] ON;
INSERT INTO[Umbraco9].[dbo].[umbracoPropertyData]([id]
      ,[versionId]
      ,[propertyTypeId]
      ,[languageId]
      ,[segment]
      ,[intValue]
      ,[decimalValue]
      ,[dateValue]
      ,[varcharValue]
      ,[textValue])
SELECT * FROM [Umbraco8].[dbo].[umbracoPropertyData]
WHERE versionId IN (SELECT ID FROM [Umbraco9].[dbo].[umbracoContentVersion]);
SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoPropertyData] OFF;

INSERT INTO[Umbraco9].[dbo].[umbracoRedirectUrl]([id]
      ,[contentKey]
      ,[createDateUtc]
      ,[url]
      ,[culture]
      ,[urlHash])
 SELECT * FROM [Umbraco8].[dbo].[umbracoRedirectUrl];

SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoRelation] ON;
INSERT INTO[Umbraco9].[dbo].[umbracoRelation] ([id]
      ,[parentId]
      ,[childId]
      ,[relType]
      ,[datetime]
      ,[comment])
SELECT * FROM [Umbraco8].[dbo].[umbracoRelation];
SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoRelation] OFF;


SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoUser] ON;
INSERT INTO[Umbraco9].[dbo].[umbracoUser] ([id]
      ,[userDisabled]
      ,[userNoConsole]
      ,[userName]
      ,[userLogin]
      ,[userPassword]
      ,[passwordConfig]
      ,[userEmail]
      ,[userLanguage]
      ,[securityStampToken]
      ,[failedLoginAttempts]
      ,[lastLockoutDate]
      ,[lastPasswordChangeDate]
      ,[lastLoginDate]
      ,[emailConfirmedDate]
      ,[invitedDate]
      ,[createDate]
      ,[updateDate]
      ,[avatar]
      ,[tourData])
 SELECT * FROM [Umbraco8].[dbo].[umbracoUser]
 WHERE id NOT IN (SELECT id FROM [Umbraco9].[dbo].[umbracoUser]);
 SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoUser] OFF;

INSERT INTO[Umbraco9].[dbo].[umbracoUser2UserGroup] ([userId]
      ,[userGroupId])
SELECT * FROM [Umbraco8].[dbo].[umbracoUser2UserGroup]
WHERE userId NOT IN (SELECT userId FROM [Umbraco9].[dbo].[umbracoUser2UserGroup]);

SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoUserGroup] ON;
INSERT INTO[Umbraco9].[dbo].[umbracoUserGroup] ([id]
      ,[userGroupAlias]
      ,[userGroupName]
      ,[userGroupDefaultPermissions]
      ,[createDate]
      ,[updateDate]
      ,[icon]
      ,[startContentId]
      ,[startMediaId])
SELECT * FROM [Umbraco8].[dbo].[umbracoUserGroup]
WHERE ID NOT IN (SELECT id FROM [Umbraco9].[dbo].[umbracoUserGroup]);
SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoUserGroup] OFF;

SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoUserStartNode] ON;
INSERT INTO[Umbraco9].[dbo].[umbracoUserStartNode] ([id]
      ,[userId]
      ,[startNode]
      ,[startNodeType])
SELECT * FROM [Umbraco8].[dbo].[umbracoUserStartNode];
SET IDENTITY_INSERT [Umbraco9].[dbo].[umbracoUserStartNode] OFF;

SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsMacro] ON;
INSERT INTO[Umbraco9].[dbo].[cmsMacro] ([id]
      ,[uniqueId]
      ,[macroUseInEditor]
      ,[macroRefreshRate]
      ,[macroAlias]
      ,[macroName]
      ,[macroCacheByPage]
      ,[macroCachePersonalized]
      ,[macroDontRender]
      ,[macroSource]
      ,[macroType])
SELECT * FROM [Umbraco8].[dbo].[cmsMacro];
SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsMacro] OFF;

SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsMacroProperty] ON;
INSERT INTO[Umbraco9].[dbo].[cmsMacroProperty] ([id]
      ,[uniquePropertyId]
      ,[editorAlias]
      ,[macro]
      ,[macroPropertySortOrder]
      ,[macroPropertyAlias]
      ,[macroPropertyName])
 SELECT * FROM [Umbraco8].[dbo].[cmsMacroProperty];
 SET IDENTITY_INSERT [Umbraco9].[dbo].[cmsMacroProperty] OFF;