MySQL合并两列并添加到一个新列中

发布于04月25日

我的MySQL表 struct 如下:

+----------------+----------------+----------+
|    zipcode     |      city      |   state  |
+----------------+----------------+----------+
|     10954      |     Nanuet     |    NY    |
+----------------+----------------+----------+

我想将上述三列合并为一列，如下所示:

+---------------------+
|      combined       |
+---------------------+
| 10954 - Nanuet, NY  |
+---------------------+

我想把这个"组合"列添加到表的末尾，而不 destruct 原来的3个字段.

推荐答案

创建列:

ALTER TABLE yourtable ADD COLUMN combined VARCHAR(50);

更新当前值:

UPDATE yourtable SET combined = CONCAT(zipcode, ' - ', city, ', ', state);

自动更新所有future 值:

CREATE TRIGGER insert_trigger
BEFORE INSERT ON yourtable
FOR EACH ROW
SET new.combined = CONCAT(new.zipcode, ' - ', new.city, ', ', new.state);

CREATE TRIGGER update_trigger
BEFORE UPDATE ON yourtable
FOR EACH ROW
SET new.combined = CONCAT(new.zipcode, ' - ', new.city, ', ', new.state);