MySQL 如何从具有文件路径的列中获取左子字符串？显示完整的文件路径字符串但排除文件名

要获取左子字符串，请使用LEFT（）和substring_index()。例如，假设文件路径是−

“/MyFile/JavaProgram/Hello.java “

在这里，我们将看到如何显示整个文件路径，除了文件名即−

/MyFile/JavaProgram/

让我们首先创建一个表−

mysql> create table DemoTable
(
   FileLocation text
);
Query OK, 0 rows affected (0.57 sec

使用insert command在表中插入一些记录−

mysql> insert into DemoTable values('/MyFile/JavaProgram/Hello.java');
Query OK, 1 row affected (0.27 sec)
mysql> insert into DemoTable values('/C/AllPrograms/animation.gif');
Query OK, 1 row affected (0.11 sec)
mysql> insert into DemoTable values('/E/FavFile/ChatProgram.java');
Query OK, 1 row affected (0.18 sec)

使用select语句从表中显示所有记录−

mysql> select *from DemoTable;

这将产生以下输出−

+--------------------------------+
| FileLocation                   |
+--------------------------------+
| /MyFile/JavaProgram/Hello.java |
| /C/AllPrograms/animation.gif   |
| /E/FavFile/ChatProgram.java    |
+--------------------------------+
3 rows in set (0.00 sec)

以下是在MySQL中获取左子字符串的查询−

mysql> select left(FileLocation,char_length(FileLocation)-char_length(substring_index(FileLocation,'/',-1))) from DemoTable;

这将产生以下输出−

+------------------------------------------------------------------------------------------------+
| left(FileLocation,char_length(FileLocation)-char_length(substring_index(FileLocation,'/',-1))) |
+------------------------------------------------------------------------------------------------+
| /MyFile/JavaProgram/                                                                           |
| /C/AllPrograms/                                                                                |
| /E/FavFile/                                                                                    |
+------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)

阅读更多：MySQL 教程