我的MySQL表具有以下结构：
+----------------+----------------+----------+ | zipcode | city | state | +----------------+----------------+----------+ | 10954 | Nanuet | NY | +----------------+----------------+----------+
我想将以上三列合并为一列，如下所示：
+---------------------+ | combined | +---------------------+ | 10954 - Nanuet, NY | +---------------------+
我想将此“组合”列添加到表的末尾而不破坏原始的3个字段。
创建列：
ALTER TABLE yourtable ADD COLUMN combined VARCHAR(50);
更新当前值：
UPDATE yourtable SET combined = CONCAT(zipcode, ' - ', city, ', ', state);
自动更新所有未来值：
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);
