Stored procedure to update column based on Min Date - sql

Question

I have been able to find similar issues to one I am having, but not that helps me to resolve!
I have a table that contains job data (tablea), schema as follows:
CREATE TABLE [dbo].[tablea](
[ID] [int] IDENTITY(1,1) NOT NULL,
[JobNo] [varchar](32) NOT NULL,
[JobDesc] [varchar](255) NULL,
[RequiredDate] [datetime] NULL
Certain jobs within this table provide components for other jobs in the same table, going forward I will call the jobs that provide components "Production Jobs" and the job receiving the components "sub jobs" - there is nothing within the table that links the rows.
There is another table (tableb)
CREATE TABLE [dbo].[tableb](
[ID] [int] IDENTITY(1,1) NOT NULL,
[JobNo] [varchar](32) NOT NULL CONSTRAINT [DF_JobProducts_JobNo] DEFAULT (''),
[SubJobNo] [varchar](32) NULL
This contains the "production job" job number (tableb.JobNo), and in the same row, the job number of the "sub job" (tableb.SubJobNo)
nb if a "production job" provides components for 7 x "sub jobs" there will be 7 x rows in tableb
I have an objective to execute a stored procedure that will update the required date column of the "production job" row of tablea with the EARLIEST date of the required date column of the associated "sub job". When executing the stored procedure, a unique identifier will be used as the variable - this will be the title of the "production job".
My attempt is as follows:
CREATE PROCEDURE [dbo].[UpdateDate]
#Title varchar(32),
AS
BEGIN
SET NOCOUNT ON;
UPDATE ta1
SET ta1.RequiredDate = ta2.RequiredDate
FROM tablea ta1
INNER JOIN tableb tb ON ta1.JobNo = tb.JobNo
INNER JOIN
(SELECT JobNo, MIN(RequiredTime)
GROUP BY JobNo
FROM tablea) ta2 ON tb.SubJobNo = ta2.JobNo
WHERE ta1.JobDesc = #Title
This has got me stumped so any help or pointers would be greatly appreciated!

Answer 1

If you are trying to say that tabalea relates to tableb then back to tablea to get to required time then just change the cte to something like this:
CREATE PROCEDURE [dbo].[UpdateDate]
#Title varchar(32),
AS
BEGIN
SET NOCOUNT ON;
;WITH cte AS (
SELECT
ta.JobNo
,MIN(ta2.RequiredTime) as NewRequiredDate
FROM
tablea ta
INNER JOIN tableb tb
ON ta.JobNo = tb.JobNo
INNER JOIN tablea ta2
ON tb.SubJobNo = ta2.JobNo
WHERE
ta.JobDesc = #Title
GROUP BY
ta.JobNo
)
UPDATE ta
SET RequiredDate = c.NewRequiredDate
FROM tablea ta
INNER JOIN cte c
ON ta.JobNo = c.JobNo