mysql中concat、RTrim、LTrim、Trim、AS

1.concat：拼接函数，可以将几个字符按照设定的格式进行拼装；

如：select concat(vend_name, ' (', vend_country, ')') from vendors ORDER BY vend_name;

+--------------------------------------------+
| concat(vend_name, ' (', vend_country, ')') |
+--------------------------------------------+
|    Anvils R Us (USA)                       |
| ACME (USA)                                 |
| Furball Inc. (USA)                         |
| Jet Set (England)                          |
| Jouets Et Ours (France)                    |
| LT Supplies (USA)                          |
+--------------------------------------------+
6 rows in set (0.00 sec)

2.RTrim：去右侧的空格；

　LTrim：去左侧的空格

　Trim:去两侧的空格；

如：select concat(Trim(vend_name), ' (', Trim(vend_country), ')') from vendors ORDER BY vend_name;

+--------------------------------------------------------+
| concat(Trim(vend_name), ' (', Trim(vend_country), ')') |
+--------------------------------------------------------+
| Anvils R Us (USA)                                      |
| ACME (USA)                                             |
| Furball Inc. (USA)                                     |
| Jet Set (England)                                      |
| Jouets Et Ours (France)                                |
| LT Supplies (USA)                                      |
+--------------------------------------------------------+
6 rows in set (0.00 sec)