sql view as per other table - sql

Question

Given the table Customers, example:
CustomerID FirstName MiddleInitial LastName
64 Abby A Garcia
65 Abby C Mehta
66 Abby E Chandra
67 Abby J Kapoor
68 Abby J Sanchez
69 Abby K Kovár
70 Abby L Sai
71 Abby M Lopez
72 Abby P Gonzalez
73 Abby P Rana
I would like to restrict the access to (table, column, row) as per definition in the other table, let's say m_Customers with definitions such as:
MetadataID Field Type Access
1 Customers table "Group1","Group2","Group3"
2 MiddleInitial column "Group1","Group3"
3 18 row "Group1","Group3"
Based on that, how do you formulate a query which ensures that if you are:
from *Group3" you can't see column MiddleInitials and row with CustomerId = 18
from "Group4" you can't see the data in Customers table
Any ideas?

Answer 1

It seems like your exclusions and inclusions are mixed. You have Group3 included with column Customers and row 18, but Group 4 not included with table Customers. Make your m_Customers table include only those that have access or only those that are restricted -- not both.
It would typically be faster and easier to manage to change your data structure for m_Customers to use a record for every group.
MetadataID Field Type Access
1 Customers table Group1
2 Customers table Group2
3 Customers table Group3
4 MiddleInitial column Group1
5 MiddleInitial column Group3
6 18 row Group1
7 18 row Group3
Here are two options; you can check for performance.
SELECT MAX(col.customerID) AS customerID, MAX(col.FirstName) AS FirstName, MAX(col.MiddleInitial) AS MiddleIntitial, MAX(col.LastName) AS LastName
FROM Customers AS c
INNER JOIN m_Customers AS mRow ON mRow.[Type] = 'row' AND mRow.CustomerID = c.Field AND mRow.Access = #group
LEFT JOIN (
SELECT
IIF(mCol.Field = 'customerID', c.customerID, NULL) AS customerID,
IIF(mCol.Field = 'Firstname', c.FirstName, NULL) AS FirstName,
IIF(mCol.Field = 'MiddleInitial', c.FirMiddleInitialstName, NULL) AS MiddleInitial,
IIF(mCol.Field = 'LastName', c.LastName, NULL) AS LastName
FROM Customers AS c
INNER JOIN m_Customers AS mCol ON mCol.[Type] = 'column' AND mCol.Field = 'MiddleInitial' AND mCol.Access = #group
) AS col ON col.customerID = c.CustomerID
GROUP BY col.customerID, col.FirstName, col.MiddleInitial, col.LastName
or
SELECT customerID.customerID, FirstName.FirstName, MiddleInitial.MiddleInitial, LastName.LastName
FROM Customers AS c
INNER JOIN m_Customers AS mRow ON mRow.[Type] = 'row' AND mRow.CustomerID = c.Field AND mRow.Access = #group
LEFT JOIN (
SELECT c.customerID
FROM Customers AS c
INNER JOIN m_Customers AS mCol ON mCol.[Type] = 'column' AND mCol.Field = 'customerID' AND mCol.Access = #group
) AS customerID ON customerID.customerID = c.customerID
LEFT JOIN (
SELECT c.customerID, c.FirstName
FROM Customers AS c
INNER JOIN m_Customers AS mCol ON mCol.[Type] = 'column' AND mCol.Field = 'FirstName' AND mCol.Access = #group
) AS FirstName ON FirstName.customerID = c.customerID
LEFT JOIN (
SELECT c.customerID, c.MiddleInitial
FROM Customers AS c
INNER JOIN m_Customers AS mCol ON mCol.[Type] = 'column' AND mCol.Field = 'MiddleInitial' AND mCol.Access = #group
) AS MiddleInitial ON MiddleInitial.customerID = c.customerID
LEFT JOIN (
SELECT c.customerID, c.LastName
FROM Customers AS c
INNER JOIN m_Customers AS mCol ON mCol.[Type] = 'column' AND mCol.Field = 'LastName' AND mCol.Access = #group
) AS LastName ON LastName.customerID = c.customerID
Consider changing the name of your column from Type to a non-reserved word.