Question

I have two tables in the database:

Article
--------------------------------------------
articleID INTEGER PRIMARY KEY AUTOINCREMENT
userID    VARCHAR

Rating
--------------------------------------------
articleID INTEGER
userID    VARCHAR
rating    INTEGER

Sample data:

Article
articleID        userID
---------------------------------
1                12345
2                23456
3                23456
4                99999
5                15678

Rating
articleID        userID        rating
--------------------------------------------
1                12345         7.5
2                12345         8.5
2                31359         7.5
1                24021         0.0
1                25012         7.5

I want to get all the articles and show if I have rated them or not. I tried and I can only get the list with rated article with this statement:

SELECT a.*, rating AS myRating FROM Article AS a 
LEFT JOIN Rating AS b
ON a.articleID = b.articleID
WHERE (b.userID is NULL || b.userID = "12345") 

How can I join the tables to get the result?

Expected output (with userID 12345)
articleID        userID        myRating
--------------------------------------------
1                12345         7.5
2                23456         8.5
3                23456         NULL
4                99999         NULL
5                15678         NULL

Answer 1

The WHERE-clause will filter out the columns where userID is not 12345 or NULL…

SELECT a.*, rating AS myRating 
FROM Article AS a 
LEFT JOIN Rating AS b
ON a.articleID = b.articleID 
AND b.userID = "12345"

Since you want to show all lines of a, put the user-id restriction in the ON clause. Now it will get all lines from A, with NULL for rating if the userid was not 12345.