SQL Server 2017

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE Job (id INT, userid INT)
INSERT INTO Job ( id ,userid)VALUES  ( 1,1)
INSERT INTO Job ( id ,userid)VALUES  ( 2,1)
INSERT INTO Job ( id ,userid)VALUES  ( 3,2)

CREATE TABLE [User] (id INT, UserName NVARCHAR (30))
INSERT INTO [User] ( id ,UserName)VALUES  ( 1,'Richard')
INSERT INTO [User] ( id ,UserName)VALUES  ( 2,'Jane')

CREATE Table Estimate (id INT, [job] INT, [GrossValue] DECIMAL (18,2))
INSERT INTO Estimate ( id ,[job], GrossValue)VALUES  ( 1,1, 100)
INSERT INTO Estimate ( id ,[job], GrossValue)VALUES  ( 2,1, 250)
INSERT INTO Estimate ( id ,[job], GrossValue)VALUES  ( 3,2, 150)
INSERT INTO Estimate ( id ,[job], GrossValue)VALUES  ( 4,3, 50)

CREATE Table AdditionalEstimate (id INT, [job] INT, [GrossValue] DECIMAL (18,2))
INSERT INTO AdditionalEstimate ( id ,[job], GrossValue)VALUES  ( 1,1, 100)
INSERT INTO AdditionalEstimate ( id ,[job], GrossValue)VALUES  ( 4,3, 200)

CREATE Table [Order] (id INT, [job] INT, ContractGiven DECIMAL (18,2), InvoicesReceived DECIMAL (18,2))
INSERT INTO [Order] ( id ,[job], ContractGiven,InvoicesReceived)VALUES  ( 1,1, 500, 300)
INSERT INTO [Order] ( id ,[job], ContractGiven,InvoicesReceived)VALUES  ( 2,1, 100, 0)
INSERT INTO [Order] ( id ,[job], ContractGiven,InvoicesReceived)VALUES  ( 3,2, 100, 0)
INSERT INTO [Order] ( id ,[job], ContractGiven,InvoicesReceived)VALUES  ( 4,3, 700, 0)

15 rows affected

UserName	(No column name)
Jane	1
Richard	2

Warning: Null value is eliminated by an aggregate or other SET operation.