T-SQL Multiple Join on 1 Table - sql-server

Question

I'm currently working on a complex T-SQL query in MS SQL Server 2012. I basically retrieve a basic list of projects, holding the ProjectId as well as the StaffVersionId (it is possible that the Staff changes throughout the project, although I hope it won't be the case :P ).
CREATE TABLE #BasicProjects
(
ProjectId INT
, StaffVersionId INT
)
Next I need to join on the ProjectData Table to get the Title of the project as well as join on the Employee Table to get the FullName of the Employee.
SELECT [P].ProjectId
, [PD].Label AS Title
, [E].Lastname + '' '' + Firstname AS Manager
, [E].Lastname + '' '' + Firstname AS Contact
FROM #BasicProjects [P]
INNER JOIN [MySchema].[ProjectData] [PD] ON [PD].ProjectDataId = [P].ProjectDataId
INNER JOIN [MySchema].[Staff] [Y] ON [Y].StaffVersionId = [P].StaffVersionId AND [Y].StaffTypeId = 3 // Manager
INNER JOIN [MySchema].[Staff] [X] ON [X].StaffVersionId = [P].StaffVersionId AND [X].StaffTypeId = 2 // Contact
INNER JOIN [dbo].[Employee] [E] ON [E].EmployeeId = [Y].EmployeeId
INNER JOIN [dbo].[Employee] [E] ON [E].EmployeeId = [X].EmployeeId
The query is kind of hard, because I have 2 kinds of staff employees 3 = Manager, 2 = Contact.
When I run my query I'm getting this error:
The correlation name 'E' is specified multiple times in a FROM clause.
Do you know how to solve this error? Or perhaps some advises on how to improve this query?
Thanks a lot!

Answer 1

You need different aliases for each join (just like you did for Staff)
SELECT [P].ProjectId
, [PD].Label AS Title
, [YE].Lastname + ' ' + YE.Firstname AS Manager
, [XE].Lastname + ' ' + XE.Firstname AS Contact
FROM #BasicProjects [P]
INNER JOIN [MySchema].[ProjectData] [PD] ON [PD].ProjectDataId = [P].ProjectDataId
INNER JOIN [MySchema].[Staff] [Y] ON [Y].StaffVersionId = [P].StaffVersionId AND [Y].StaffTypeId = 3 // Manager
INNER JOIN [MySchema].[Staff] [X] ON [X].StaffVersionId = [P].StaffVersionId AND [X].StaffTypeId = 2 // Contact
INNER JOIN [dbo].[Employee] [YE] ON [YE].EmployeeId = [Y].EmployeeId
INNER JOIN [dbo].[Employee] [XE] ON [XE].EmployeeId = [X].EmployeeId