SQL Query - Complex query between tables - sql

Question

I currently have the 5 following tables. Each Site has (1 or Many) Project Managers as well as (1 or Many) Site_Supervisors. A Project Manager / Site Supervisor can be assigned to many sites
I currently have a working query:
SELECT Sites.Site_Name, Sites.Site_Street_Address, Sites.Site_Suburb, Sites.Site_State, Sites.Site_Postcode, Sites.Site_Region, Sites.Completed, Project_Managers.First_Name AS PM_First_Name, Project_Managers.Last_Name AS PM_Last_Name, Site_Supervisors.First_Name AS SS_First_Name, Site_Supervisors.Last_Name AS SS_Last_Name, Sites.Date_Started
FROM Site_Site_Supervisors INNER JOIN
Site_Supervisors ON Site_Site_Supervisors.Site_Supervisor_ID = Site_Supervisors.Site_Supervisor_ID RIGHT OUTER JOIN
Sites ON Site_Site_Supervisors.Site_ID = Sites.Site_ID LEFT OUTER JOIN
Project_Managers INNER JOIN
Site_Project_Managers ON Project_Managers.Project_Manager_ID = Site_Project_Managers.Project_Manager_ID ON
Sites.Site_ID = Site_Project_Managers.Site_ID
WHERE (Sites.Completed = 0)
ORDER BY Sites.Site_Name
Which gives me the desired output, which i then work with in my code.
I am wanting to make a change to the query, where instead of outputting the:
Project_Managers.First_Name AS PM_First_Name
Project_Managers.Last_Name AS PM_Last_Name
instead i replace these with:
Project_Managers.First_Name where the corresponding Site_Project_Managers.Primary_Contact = True AS PM_First_Name
Project_Managers.Last_Name where the corresponding Site_Project_Managers.Primary_Contact = True AS PM_Last_Name
Project_Managers.First_Name where the corresponding Site_Project_Managers.Primary_Contact = False AS AssistantPM_First_Name
Project_Managers.Last_Name where the corresponding Site_Project_Managers.Primary_Contact = False AS AssistantPM_Last_Name
To perform this query is beyond my SQL skillset at this time, so i am hoping one of you can provide me with the correct query to use and or some guidance
Thanks
Sites
[Site_ID] [int] IDENTITY(1,1) NOT NULL (PK),
[Site_Name] [varchar](50) NOT NULL,
[Site_Street_Address] [varchar](50) NULL,
[Site_Suburb] [varchar](50) NULL,
[Site_State] [varchar](50) NULL,
[Site_Postcode] [varchar](10) NULL,
[Site_Region] [varchar](50) NULL,
[Date_Started] [datetime] NULL,
[Completed] [bit] NOT NULL
Project_Managers
[Project_Manager_ID] [int] IDENTITY(1,1) NOT NULL (PK),
[First_Name] [varchar](50) NOT NULL,
[Last_Name] [varchar](50) NOT NULL,
[Phone_Number] [varchar](50) NULL,
[Email_Address] [varchar](50) NULL,
[Currently_Employed] [bit] NOT NULL,
CONSTRAINT [PK_Project_Managers] PRIMARY KEY CLUSTERED
Site_Supervisors
[Site_Supervisor_ID] [int] IDENTITY(1,1) NOT NULL (PK),
[First_Name] [varchar](50) NOT NULL,
[Last_Name] [varchar](50) NOT NULL,
[Phone_Number] [varchar](50) NULL,
[Email_Address] [varchar](50) NULL,
[Currently_Employed] [bit] NOT NULL,
CONSTRAINT [PK_Site_Supervisors_1] PRIMARY KEY CLUSTERED
Site_Project_Managers
[Site_ID] [int] NOT NULL (PK),
[Project_Manager_ID] [int] NOT NULL (PK),
[Primary_Contact] [bit] NULL,
[Alerts] [bit] NULL,
CONSTRAINT [PK_Site_Project_Managers] PRIMARY KEY CLUSTERED
Site_Site_Supervisors
[Site_ID] [int] NOT NULL (PK),
[Site_Supervisor_ID] [int] NOT NULL (PK),
[Primary_Contact] [bit] NULL,
[Alerts] [bit] NULL,
CONSTRAINT [PK_Site_Site_Supervisors] PRIMARY KEY CLUSTERED

Answer 1

Assumed you are using MySql and you may use the CASE or inline IF ELSE to get the desired output that you want
SELECT Sites.Site_Name,
Sites.Site_Street_Address,
Sites.Site_Suburb,
Sites.Site_State,
Sites.Site_Postcode,
Sites.Site_Region,
Sites.Completed,
CASE Site_Project_Managers.Primary_Contact
WHEN true THEN Project_Managers.First_Name
END AS PM_First_Name,
CASE Site_Project_Managers.Primary_Contact
WHEN true THEN Project_Managers.Last_Name
END AS PM_Last_Name,
CASE Site_Project_Managers.Primary_Contact
WHEN false THEN Project_Managers.First_Name
END AS AssistantPM_First_Name,
CASE Site_Project_Managers.Primary_Contact
WHEN false THEN Project_Managers.Last_Name
END AS AssistantPM_Last_Name,
Site_Supervisors.First_Name AS SS_First_Name,
Site_Supervisors.Last_Name AS SS_Last_Name,
Sites.Date_Started
FROM Site_Site_Supervisors
INNER JOIN Site_Supervisors
ON Site_Site_Supervisors.Site_Supervisor_ID = Site_Supervisors.Site_Supervisor_ID
RIGHT OUTER JOIN Sites
ON Site_Site_Supervisors.Site_ID = Sites.Site_ID
LEFT OUTER JOIN Project_Managers
INNER JOIN Site_Project_Managers
ON Project_Managers.Project_Manager_ID = Site_Project_Managers.Project_Manager_ID
ON Sites.Site_ID = Site_Project_Managers.Site_ID
WHERE (Sites.Completed = 0)
ORDER BY Sites.Site_Name