Trying to get the right SQL Query (Joins) - sql

Question

I've been trying to join a couple tables to get the right result.
The problem is its returning some NULL values where this shouldn't be the case.
EP.ProductId, CreateDate, IsproductActivated and Subject are returning a Null Value.I've noticed it That DossierID and dossier will return a value when I make a right join as stated below.
Could anyone help me with my case?
SELECT
EP.ProductId AS [ProductId]
,MAX(EP.CreateDate) AS [CreateDate]
,EP.IsProductActivated AS [IsProductActivated]
,PC.EntityId AS [DossierID]
,PC.EntityDiscriminator AS [EntityDiscriminator]
,PDCP.Name AS [Subject]
,D.Name AS [Dossier]
FROM
[tblEntityProduct] AS EP
LEFT JOIN .tblPDCProduct AS PDCP
ON PDCP.id = EP.Productid
LEFT JOIN
[tblProductContainerContent] AS PCC
ON PCC.EntityProductId = EP.ProductId
RIGHT JOIN
[tblProductContainer] AS PC
ON PC.Id = PCC.Productcontainerid
LEFT JOIN
[tblDossier] AS D
ON D.Id = PC.Entityid
WHERE PC.EntityId = 2803
GROUP BY EP.Productid
,IsProductActivated
,EntityId
,EntityDiscriminator
,PDCP.name
,D.name
The picture below shows the result of the above query. I want the values it suppose to have instead of the NULL

Answer 1

use inner join to avoid getting null values, because The LEFT JOIN keyword returns all records from the left table (table1), and the matched records from the right table (table2). The result is NULL from the right side, if there is no match. for right join opposite is true of left join
SELECT
EP.ProductId AS [ProductId]
,MAX(EP.CreateDate) AS [CreateDate]
,EP.IsProductActivated AS [IsProductActivated]
,PC.EntityId AS [DossierID]
,PC.EntityDiscriminator AS [EntityDiscriminator]
,PDCP.Name AS [Subject]
,D.Name AS [Dossier]
FROM
[tblEntityProduct] AS EP
JOIN .tblPDCProduct AS PDCP
ON PDCP.id = EP.Productid
JOIN
[tblProductContainerContent] AS PCC
ON PCC.EntityProductId = EP.ProductId
JOIN
[tblProductContainer] AS PC
ON PC.Id = PCC.Productcontainerid
JOIN
[tblDossier] AS D
ON D.Id = PC.Entityid
WHERE PC.EntityId = 2803
GROUP BY EP.Productid
,IsProductActivated
,EntityId
,EntityDiscriminator
,PDCP.name
,D.name

Answer 2

I hate right-joins. They are basically a REQUIRE THIS TABLE regardless of the others leading up to it. Instead, I reversed the query to put the REQUIRED Table in the first position, then LEFT-JOIN to the underlying. Now, based on the structure / join, I would THINK that you start with a product container -- will always exist. Each product container has stuff in it (ProductContainerContent). Then, each content item IS an entity product to get its description. Each container has its own Dossier which may (or not) be assigned at the time the container is being prepared. If I am accurate, most of the LEFT-JOINs should just be standard (inner) JOINs, but lets see what this does against your data.
SELECT
EP.ProductId,
MAX(EP.CreateDate) CreateDate,
EP.IsProductActivated,
PC.EntityId DossierID,
PC.EntityDiscriminator,
PDCP.Name Subject,
D.Name Dossier
FROM
tblProductContainer PC
LEFT JOIN tblProductContainerContent PCC
ON PC.Id = PCC.Productcontainerid
LEFT JOIN tblEntityProduct EP
ON PCC.EntityProductId = EP.ProductId
LEFT JOIN tblPDCProduct PDCP
ON EP.Productid = PDCP.id
LEFT JOIN tblDossier D
ON PC.Entityid = D.Id
WHERE
PC.EntityId = 2803
GROUP BY
EP.Productid,
IsProductActivated,
EntityId,
EntityDiscriminator,
PDCP.name,
D.name