1.ASCII(char)返回字符的ASCII值。
2.1个字符=8个字节(byte)bit_length(str)表示的是返回字符串的字节长度即比特长度一个汉字=2字符(16个字节)
3.concat(s1,s2..sn)即将s1,s2..sn连接成字符串。4.concat(sep,s1,s2,..sn)将连接的字符串用分隔符separater分
开连接。mysql> select concat_ws('-','A','B','C','LINING');
+-------------------------------------+
| concat_ws('-','A','B','C','LINING') |
+-------------------------------------+
| A-B-C-LINING                        |
+-------------------------------------+
1 row in set (0.01 sec)5.insert(str,1(下标从1开始),要被替换字符串长度,要替换的字
符串)表示字符串从下标为1的位置开始查询，如果要被替换的字
符串长度为几，则用参数四的字符串进行替换。mysql> select insert('abcdefg',1,3,'AB');
+----------------------------+
| insert('abcdefg',1,3,'AB') |
+----------------------------+
| ABdefg                     |
+----------------------------+
1 row in set (0.00 sec)
6.find_in_set(要查找的字符串,字符串列表)，比如find_in_set('2','1,2,3,4,5,6,7')这是返回数字2的下标是2说明下标的位置从1开始！！mysql> select find_in_set('e','d,2,e,{,u,},5');
+----------------------------------+
| find_in_set('e','d,2,e,{,u,},5') |
+----------------------------------+
|                                3 |
+----------------------------------+
1 row in set (0.00 sec)mysql> select find_in_set('3','1,2,3,4,5,6,7');
+----------------------------------+
| find_in_set('3','1,2,3,4,5,6,7') |
+----------------------------------+
|                                3 |
+----------------------------------+
1 row in set (0.00 sec)7.LCASE(str)或者LOWER(str)将字符串大写改变为小写！8.left(str,数字)表示返回字符串左边的字符个数。mysql> select left('abedfdafd',4);
+---------------------+
| left('abedfdafd',4) |
+---------------------+
| abed                |
+---------------------+
1 row in set (0.00 sec)
9.length(str)返回字符串str的个数。如果是中文，则返回的也
是字符数  即18个汉字=36个字符。10。GROUP_CONCAT(col) 返回属于一组的列值组成的结构。mysql> select group_concat(num1) from tb_test;
+--------------------+
| group_concat(num1) |
+--------------------+
| -24,14,-13,13,11   |
+--------------------+
1 row in set (0.00 sec)