取mysql的子字符串，怎么总是不对呢？

Question

SELECT LENGTH("'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕然','',") AS tmplength;
-----88
SELECT LEFT("'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕然','',", 87) AS tmpsubstr;
--'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕然','',本来我的目的是想去掉最后那个字符，结果还是不对，子字符串和源字符串("'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕然','',")  
仍然是一模一样的。请问到底是怎么回事？

Answer 1

我这里没有问题。
mysql> SELECT LEFT("'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕
然','',", 87) AS tmpsubstr;
+----------------------------------------------------------------------------------------+
| tmpsubstr                                                                              |
+----------------------------------------------------------------------------------------+
| 'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕然','', |
+----------------------------------------------------------------------------------------+
1 row in set (0.16 sec)

Answer 2

mysql> select length('毕然');
+----------------+
| length('毕然') |
+----------------+
|              6 |
+----------------+
1 row in setmysql> select left('毕然',2);
+----------------+
| left('毕然',2) |
+----------------+
| 毕然           |
+----------------+
1 row in set

Answer 3

mysql> SELECT LENGTH("'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕然','',") AS tmplen
gth;
+-----------+
| tmplength |
+-----------+
|        86 |
+-----------+
1 row in set (0.00 sec)mysql> SELECT LEFT("'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕
    "> 然','',", 87) AS tmpsubstr;
+-----------------------------------------------------------------------------------------+
| tmpsubstr                                                                               |
+-----------------------------------------------------------------------------------------+
| 'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕
然','', |
+-----------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

Answer 4

'U000000008','VICKY','96E79218965EB72C92A549DD5A330112','R000000002','6666','毕然','',这个字符串只有86个字节！