Trying To Avoid A Cursor...

Happy new year to all! Now a question...

I added a new column to StagePayments table - Activity - which is supposed to end up being the same as the JobActivityID from the JobActivities table. Basically, I need to get JobActivities (JA) info and put it in the StagePayment (SP) column. Problem is there are duplicate JA/Descriptions and SP/Activities, so what I need is to take the first sequence SP/Activity and grab the first JA/JobActivityID that matches for a particular JobID. Then get the next one of each and so on and so on...

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Tables...

CREATE TABLE [dbo].[StagePayment] (
[PaymentID] [uniqueidentifier] NOT NULL ,
[JobID] [uniqueidentifier] NOT NULL ,
[Paid] [bit] NOT NULL ,
[Sequence] [smallint] NOT NULL ,
[Amount] [decimal](10, 2) NOT NULL ,
[Comment] [varchar] (2000) COLLATE SQL_Latin1_General_CP437_BIN NULL ,
[Activity] [varchar] (30) COLLATE SQL_Latin1_General_CP437_BIN NULL ,
[ActivityID] [uniqueidentifier] NULL
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[StagePayment] WITH NOCHECK ADD
CONSTRAINT [PK__StagePayment__457442E6] PRIMARY KEY CLUSTERED
(
[PaymentID]
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[StagePayment] WITH NOCHECK ADD
CONSTRAINT [DF__StagePayme__Paid__4668671F] DEFAULT (0) FOR [Paid]
GO

CREATE INDEX [IX_StagePayment] ON [dbo].[StagePayment]([JobID], [Sequence]) ON [PRIMARY]
GO

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CREATE TABLE [dbo].[JobActivities] (
[JobActivityID] [uniqueidentifier] NOT NULL ,
[JobID] [uniqueidentifier] NOT NULL ,
[Sequence] [smallint] NOT NULL ,
[Activity_Status] [char] (1) COLLATE SQL_Latin1_General_CP437_BIN NOT NULL ,
[Description] [char] (30) COLLATE SQL_Latin1_General_CP437_BIN NOT NULL ,
[PlanStartDate] [datetime] NULL ,
[PlanEndDate] [datetime] NULL ,
[ActEndDate] [datetime] NULL ,
[AmountDue] [decimal](10, 2) NOT NULL ,
[CanDelete] [bit] NOT NULL ,
[Comments] [varchar] (2000) COLLATE SQL_Latin1_General_CP437_BIN NULL
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[JobActivities] WITH NOCHECK ADD
CONSTRAINT [PK_JobActivity] PRIMARY KEY CLUSTERED
(
[JobActivityID]
) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

ALTER TABLE [dbo].[JobActivities] WITH NOCHECK ADD
CONSTRAINT [DF_JobActivities_JobActivityID] DEFAULT (newid()) FOR [JobActivityID]
GO

CREATE INDEX [IX_JobActivity] ON [dbo].[JobActivities]([JobID]) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

CREATE INDEX [IX_JobActivity_1] ON [dbo].[JobActivities]([JobID], [Activity_Status]) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

CREATE INDEX [IX_JobActivity_2] ON [dbo].[JobActivities]([JobID], [ActEndDate]) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

CREATE INDEX [IX_JobActivities] ON [dbo].[JobActivities]([JobID], [PlanEndDate]) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

CREATE INDEX [JobActivities53] ON [dbo].[JobActivities]([JobID], [Description], [ActEndDate]) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

CREATE INDEX [JobActivities50] ON [dbo].[JobActivities]([JobID], [Description], [PlanEndDate], [ActEndDate]) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

CREATE INDEX [IX_JobActivities_6] ON [dbo].[JobActivities]([JobActivityID], [Activity_Status], [Description]) WITH FILLFACTOR = 90 ON [PRIMARY]
GO

CREATE INDEX [IX_JobActivities_1] ON [dbo].[JobActivities]([JobID], [Sequence], [Description], [JobActivityID]) ON [PRIMARY]
GO

CREATE INDEX [IX_JobActivities_2] ON [dbo].[JobActivities]([JobID], [Sequence], [ActEndDate]) ON [PRIMARY]
GO

ALTER TABLE [dbo].[JobActivities] ADD
CONSTRAINT [FK_JobActivity_Job] FOREIGN KEY
(
[JobID]
) REFERENCES [dbo].[Jobs] (
[JobID]
) ON DELETE CASCADE
GO

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My example for one single JobID...

In JA -

JobActivityID Seq Description
34969C69-FF70-4313-91CC-43921DB3D74D 18 FOLLOWUP
48ACFEEE-3349-4F16-83E0-58F9B19E28E5 16 INSTALL
22507D44-6D0D-42DE-A211-9C23FDFCD19D 5 PLOTPLAN
BA88D04E-EBAE-40DB-A2C9-F909463D7F22 1 THANKU
83C48207-895B-4775-A62D-07059D8DEB62 10 NOTCUST
DBB8DF00-E26B-4E6F-9482-08E8CFE1588D 11 ROOMORD
BF621E91-E819-4F84-B507-0AA644D5C3F6 0 DWNPAY
6F595880-59D9-4E55-845D-19B477E8B179 2 THANKU
86D0A650-3B72-47E1-BDC2-2CA177DC3D53 12 NOTCSTRM
B0ABCC4C-A626-41C2-890C-3B9580326774 13 ROOMREC
F131C6FF-A86C-4527-A580-60FF7D3F0164 19 1YRFLWUP
7132625C-8E8B-4748-9176-6F06E8D0F20F 17 ARCMNT
AE06A938-323B-46EA-BA11-7D17B0985ACC 15 24HRCALL
DBEF21DF-35DA-48DE-8BF5-7F4A0EC0FA7A 14 24HRCALL
EBC15C77-95D5-4C42-AD88-861F9DD7688B 9 RECPERMT
97D3D755-4B6F-4564-842B-A06945AA8890 8 SUBPERMT
CAACAACA-3B97-41D5-9A4A-A4E3E963D0BF 6 SUBCAD
0C3CB2E0-F4E9-43CD-81E4-ACE9F4022033 3 PHONCALL
42D498BE-308A-413E-965D-ADE7A7A21B97 4 MEASURE
7654C5E3-BED5-4F78-ADC8-DD4E283ADDEE 7 RECCAD

In SP -

Seq Activity ActivityID
1 NULL
2 24HRCALL
3 24HRCALL
4 INSTALL

I need to get SP to end up looking like this -

Seq Activity ActivityID
1 NULL NULL
2 24HRCALL DBEF21DF-35DA-48DE-8BF5-7F4A0EC0FA7A
3 24HRCALL AE06A938-323B-46EA-BA11-7D17B0985ACC
4 INSTALL 48ACFEEE-3349-4F16-83E0-58F9B19E28E5


I have tried various versions of this...
begin transaction
update StagePayment
set Activity = (Select J.JobActivityID
from JobActivities J (nolock)
inner join StagePayment SP (nolock) on J.JobID = SP.JobID and J.Description = SP.Activity)
where Activity is not NULL

way too basic as I get this error...

Server: Msg 512, Level 16, State 1, Line 2
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
The statement has been terminated.

I know somehow I have to get the duplicate Activities in the same sequence as the Descriptions, but that's where I'm stuck?!?

If anyone is able to offer suggestions on how to get this to update correctly, I'd be very happy to hear about it!
Thanks in advance!
Tiffanie