MySQL Unknown column in where clause? - mysql

Question

I have two databases.
One is called INFO with three tables (Stories, Comments, Replies)
Stories has the following fields
+--------------+----------------+------+-----+---------------------+-----------------------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+----------------+------+-----+---------------------+-----------------------------+
| storyID | int(11) | NO | PRI | NULL | |
| originalURL | varchar(500) | YES | | NULL | |
| originalDate | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP |
| numDiggs | int(11) | YES | | NULL | |
| numComments | int(11) | YES | | NULL | |
| diggURL | varchar(500) | YES | | NULL | |
| rating | varchar(50) | YES | | NULL | |
| title | varchar(200) | YES | | NULL | |
| summary | varchar(10000) | YES | | NULL | |
| uploaderID | varchar(50) | YES | | NULL | |
| imageURL | varchar(500) | YES | | NULL | |
| category1 | varchar(50) | YES | | NULL | |
| category2 | varchar(50) | YES | | NULL | |
| uploadDate | timestamp | NO | | 0000-00-00 00:00:00 | |
| num | int(11) | YES | | NULL | |
+--------------+----------------+------+-----+---------------------+-----------------------------+
Another database is called Data with one table (User). Fields shown below:
+-------------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+-------------+------+-----+---------+-------+
| userID | varchar(50) | NO | PRI | NULL | |
| numStories | int(11) | YES | | NULL | |
| numComments | int(11) | YES | | NULL | |
| numReplies | int(11) | YES | | NULL | |
| numStoryDiggs | int(11) | YES | | NULL | |
| numCommentReplies | int(11) | YES | | NULL | |
| numReplyDiggs | int(11) | YES | | NULL | |
| numStoryComments | int(11) | YES | | NULL | |
| numStoryReplies | int(11) | YES | | NULL | |
+-------------------+-------------+------+-----+---------+-------+
User.userID is full of thousands of unique names. All other fields are currently NULL. The names in User.userID correspond to the names in Stories.uploaderID.
I need to, for each userID in User, count the number of stories uploaded from (i.e. num) Stories for the corresponding name and insert this value into User.numStories.
The query which I have come up with (which produces an error) is:
INSERT INTO DATA.User(numStories)
SELECT count(num)
FROM INFO.Stories
WHERE INFO.Stories.uploaderID=DATA.User.userID;
The error I get when running this query is
Unknown column 'DATA.User.userID' in 'where clause'
Sorry if this is badly explained. I will try and re-explain if need be.

Answer 1

You aren't creating new entries in the User table, you're updating existing ones. Hence, insert isn't the right syntax here, but rather update:
UPDATE DATA.User u
JOIN (SELECT uploaderID, SUM(num) AS sumNum
FROM INFO.Stories
GROUP BY uploadedID) i ON i.uploaderID = u.userID
SET numStories = sumNum
EDIT:
Some clarification, as requested in the comments.
The inner query sums the num in Stories per uploaderId. The updates statement updates the numStories in User the the calculated sum of the inner query of the matching id.