如何从带有文件路径的列中获取MySQL中的左子字符串？显示整个文件路径字符串，不包括文件名？

要获得左子字符串，请使用LEFT()以及substring_index()。例如，假设文件路径为-

“/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-

create table DemoTable
(
   FileLocation text
);
insert into DemoTable values('/C/AllPrograms/animation.gif');
insert into DemoTable values('/E/FavFile/ChatProgram.java');

使用select语句显示表中的所有记录-

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-

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)