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)
mysql中concat、RTrim、LTrim、Trim、AS
原文：https://www.cnblogs.com/weiyouqing/p/14690300.html