Problem creating a view containing lookup tables - sql

Question

should be simple enough but it's causing me a couple of issues.
I have a data set similar to the following:
User
UserID
Name
Age
UserPropertyValues
UserID
PropertyCodeValueID
PropertyCodes
PropertyCodeID
PropertyCodeName
PropertyCodeValues
PropertyCodeValueID
PropertyCodeID
PropertValue
Now let's assume the tables contain the following data:
1 John 25
2 Sarah 34
1 2
1 3
2 1
2 3
1 FavColour
2 CarMake
3 PhoneType
1 1 Blue
2 1 Yellow
3 2 Ford
4 3 Mobile
5 3 Landline
Now from this I'm looking to create a view to return the User details, as well as the property values for Property code 1 and 2 like so:
John 25 Yellow Ford
Sarah 34 Blue Ford
The queries I have tried so far tend to return repeating rows of data :
John 25 Yellow
John 25 Ford
Sarah 34 Blue
Sarah 34 Ford
Any help is appreciated, thank you all in advance.

Answer 1

Input data:
DECLARE #User TABLE (UserID INT, Name VARCHAR(10), Age INT)
INSERT INTO #User
SELECT 1, 'John', 25 UNION
SELECT 2, 'Sarah', 34
DECLARE #UserPropertyValues TABLE(UserID INT, PropertyCodeValueID INT)
INSERT INTO #UserPropertyValues
SELECT 1, 2 UNION
SELECT 1, 3 UNION
SELECT 2, 1 UNION
SELECT 2, 3
DECLARE #PropertyCodes
TABLE (PropertyCodeID INT, PropertyCodeName VARCHAR(10))
INSERT INTO #PropertyCodes
SELECT 1, 'FavColour' UNION
SELECT 2, 'CarMake' UNION
SELECT 3, 'PhoneType'
DECLARE #PropertyCodeValues TABLE (PropertyCodeValueID INT,
PropertyCodeID INT, PropertValue VARCHAR(10))
INSERT INTO #PropertyCodeValues
SELECT 1, 1, 'Blue' UNION
SELECT 2, 1, 'Yellow' UNION
SELECT 3, 2, 'Ford' UNION
SELECT 4, 3, 'Mobile' UNION
SELECT 5, 3, 'Landline'
If two properties is all that you need in result, and each user have those properties, then try this:
SELECT U.Name, U.Age, PCVFC.PropertValue, PCVCM.PropertValue
FROM #User U
INNER JOIN #UserPropertyValues UPVFC ON U.UserID = UPVFC.UserID
INNER JOIN #PropertyCodeValues PCVFC
ON UPVFC.PropertyCodeValueID = PCVFC.PropertyCodeValueID
AND PCVFC.PropertyCodeID = 1
INNER JOIN #UserPropertyValues UPVCM ON U.UserID = UPVCM.UserID
INNER JOIN #PropertyCodeValues PCVCM
ON UPVCM.PropertyCodeValueID = PCVCM.PropertyCodeValueID
AND PCVCM.PropertyCodeID = 2
[edit] But to handle possible NULL values better use this:
SELECT U.Name, U.Age, FC.PropertValue, CM.PropertValue
FROM #User U
LEFT JOIN (
SELECT UserID, PropertValue FROM #UserPropertyValues UPV
INNER JOIN #PropertyCodeValues PCV
ON UPV.PropertyCodeValueID = PCV.PropertyCodeValueID
AND PCV.PropertyCodeID = 1
) FC ON U.UserID = FC.UserID
LEFT JOIN (
SELECT UserID, PropertValue FROM #UserPropertyValues UPV
INNER JOIN #PropertyCodeValues PCV
ON UPV.PropertyCodeValueID = PCV.PropertyCodeValueID
AND PCV.PropertyCodeID = 2
) CM ON U.UserID = CM.UserID

Answer 2

What you really need to is abandon this type of database design as soon as humanly possible. It will never be either effective of efficient. To get three types of values you have to join to the table three times. Once you have 30 or forty differnt types of information, you will need to join to the table that many times (and left joins at that). Further everytime you want any information you will need to join to this table. I see this as creating a major locking issue in your database. The people who originally designed one of the databases I work with did this and caused a huge performance issue when the company grew from having one or two customers to the largest in our industry.
If the properties are ones that will likely only have one realted records per person, put them into the user table. If they will have multiple records then create a separate table for each type of information (one for hones, one for email, one for cartype, etc.) Since the information you will eventually want to collect will usually be more than the simple value and differnt for each type of information they must be in separate tables. Then when you only need to see one value (say phone number but not email) you join to just that table and you aren't interfeing with people trying to access email but not phone number. And if you have a yellow ford or white Honda, it will be stored in only one record in the auto table rather than two property records in your design.

Answer 3

SELECT
u.[Name],
u.Age,
pcv1.PropertValue,
pcv2.PropertValue
FROM
Users u
LEFT JOIN
( UserPropertyValues upv1
JOIN PropertyCodeValues pcv1 ON
upv1.PropertyCodeValueID = pcv1.PropertyCodeValueID
AND pcv1.PropertyCodeID = 1
)
ON upv1.UserID = u.UserID
LEFT JOIN (
UserPropertyValues upv2
JOIN PropertyCodeValues pcv2 ON
upv2.PropertyCodeValueID = pcv2.PropertyCodeValueID
AND pcv2.PropertyCodeID = 2
)
ON upv2.UserID = u.UserID
Edit : I renamed user to users
Edit2 : Allow for null (not entered values)