MySQL字串函式substring：字串擷取

MySQL 字串擷取函式：left(), right(), substring(), substring_index()。還有 mid(), substr()。其中，mid(), substr() 等價於 substring() 函式，substring() 的功能非常強大和靈活。

1. 字串擷取：left(str, length)

mysql> select left("example.com", 3);

+-------------------------+

| left("example.com", 3) |

+-------------------------+

| exa |

+-------------------------+

2. 字串擷取：right(str, length)

mysql> select right("example.com", 3);

+--------------------------+

| right("example.com", 3) |

+--------------------------+

| com |

+--------------------------+

例項：

#查詢某個欄位後兩位字元

select right(last3, 2) as last2 from historydata limit 10;

#從應該欄位取後兩位字元更新到另外一個欄位

update `historydata` set `last2`=right(last3, 2);