MYSQL更新表，如果記錄存在

Question

好了，所以我有一個表叫cities的列id,city,state,county,zip_code,url

然後我有第二個表稱爲us_url的列：id, url, city, state

的cities表有city和獨特的關鍵state以防止重複（因此，如果我導入新記錄，如果城市+狀態組合已存在，則跳過它）。

現在，us_url只是暫時的。我想將該表中的數據複製到cities表中。因此，如果cities中不存在city & state組合，請從us_url表中插入新記錄。如果確實存在，請使用us_url.url值更新cities.url列。

我已經試過這樣：

INSERT INTO cities (id, city, state, county, zip_code, url) 
      VALUES(,us_url.city,us_url.state,,url) 
      ON DUPLICATE KEY UPDATE url=VALUES(url); 

但是，這給了我一個語法錯誤，我甚至不知道這是正確的。

我希望這是有道理的。任何幫助是極大的讚賞。

Answer 1

insert into cities (id,city, state,url) (select id,city,state,url from us_url) on duplicate key update url=VALUES(url); 

應該做的伎倆：

mysql> select * from cities; 
+------+------+-------+---------+----------+------+ 
| id | city | state | country | zip_code | url | 
+------+------+-------+---------+----------+------+ 
| 1 | 2 | 3  | 4  | 5  | 6 | 
+------+------+-------+---------+----------+------+ 
1 row in set (0.00 sec) 

mysql> select * from us_url; 
+------+------+------+-------+ 
| id | url | city | state | 
+------+------+------+-------+ 
| 1 | 10 | 2 | 3  | 
| 2 | 11 | 3 | 4  | 
+------+------+------+-------+ 
2 rows in set (0.00 sec) 

mysql> insert into cities (id,city, state,url) (select id,city,state,url from us_url) on duplicate key update url=VALUES(url); 
Query OK, 1 row affected (0.01 sec) 
Records: 2 Duplicates: 0 Warnings: 0 

mysql> select * from cities; 
+------+------+-------+---------+----------+------+ 
| id | city | state | country | zip_code | url | 
+------+------+-------+---------+----------+------+ 
| 1 | 2 | 3  | 4  | 5  | 10 | 
| 2 | 3 | 4  | NULL | NULL  | 11 | 
+------+------+-------+---------+----------+------+ 
2 rows in set (0.00 sec) 

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