问题
How can I update the table based on the results of the previous query?
The original query (big thanks to GMB) can find any items in address (users table) that have a match in address (address_effect table).
From the result of this query, I want to find the count of address in the address_effect table and add it into a new column in the table “users”. For example, john doe has a match with idaho and usa in the address column so it’ll show a count of ‘2’ in the count column.
Fyi, I'm testing this on my local system with XAMPP (using MariaDB).
user table
+--------+-------------+---------------+--------------------------+--------+
| ID | firstname | lastname | address | count |
| | | | | |
+--------------------------------------------------------------------------+
| 1 | john | doe |james street, idaho, usa | |
| | | | | |
+--------------------------------------------------------------------------+
| 2 | cindy | smith |rollingwood av,lyn, canada| |
| | | | | |
+--------------------------------------------------------------------------+
| 3 | rita | chatsworth |arajo ct, alameda, cali | |
| | | | | |
+--------------------------------------------------------------------------+
| 4 | randy | plies |smith spring, lima, peru | |
| | | | | |
+--------------------------------------------------------------------------+
| 5 | Matt | gwalio |park lane, atlanta, usa | |
| | | | | |
+--------------------------------------------------------------------------+
address_effect table
+---------+----------------+
|address |effect |
+---------+----------------+
|idaho |potato, tater |
+--------------------------+
|canada |cold, tundra |
+--------------------------+
|fremont | crowded |
+--------------------------+
|peru |alpaca |
+--------------------------+
|atlanta |peach, cnn |
+--------------------------+
|usa |big, hard |
+--------+-----------------+
回答1:
Notice: I checked it in MySQL, but not in MariaDB.
The count column of users table may be able to be updated using UPDATE statement with INNER JOIN. Then you can use a query that modifies the original query to use "GROUP BY".
UPDATE users AS u
INNER JOIN
(
-- your original query modified
SELECT u.ID AS ID, count(u.ID) AS count
FROM users u
INNER JOIN address_effect a
ON FIND_IN_SET(a.address, REPLACE(u.address, ', ', ','))
GROUP BY u.ID
) AS c ON u.ID=c.ID
SET u.count=c.count;
回答2:
Use a correlated subquery which returns the number of matches:
UPDATE user u
SET u.count = (
SELECT COUNT(*)
FROM address_effect a
WHERE FIND_IN_SET(a.address, REPLACE(u.address, ', ', ','))
)
See the demo.
Results:
> ID | firstname | lastname | address | count
> -: | :-------- | :--------- | :------------------------- | ----:
> 1 | john | doe | james street, idaho, usa | 2
> 2 | cindy | smith | rollingwood av,lyn, canada | 1
> 3 | rita | chatsworth | arajo ct, alameda, cali | 0
> 4 | randy | plies | smith spring, lima, peru | 1
> 5 | Matt | gwalio | park lane, atlanta, usa | 2
来源：https://stackoverflow.com/questions/62964855/updating-table-based-on-the-results-of-previous-query