如何在SQLIte中获取子字符串？ [英] How to get substring in SQLIte?

问题描述

我从SQLite数据库中检索了大量的数据。当检索我将它映射到我的应用程序中的不同视图。在我的表中有一个文本字段，我不想从中获取完整的文本，只是前n个字符。所以如果我的查询是例如：

 从文章中选择描述id = '29'; 
  

那么如何从描述中获取子字符串？感谢

解决方案

使用 substr
$ b

从核心功能列表：

substr（X，Y，Z）

Y）

substr（X，Y，Z）函数返回一个子字符串的输入字符串 X 表示
以 Y 字符开头，并且 Z 个字符。如果 Z 是
省略，则 substr（X，Y）返回所有字符b $ b string X 以第Y个开头。 X 的最左边的字符是
number 1.如果 Y 子串
通过从右而不是左计数来找到。如果 Z 是
negative，则 Y之前的 abs（Z） 字符是
返回。如果 X 是字符串，则字符索引引用实际的
UTF-8字符。如果 X 是BLOB，则索引引用字节。

I retrieve quite a lot of data from SQLite database. When retrieving I map it to different views in my application. There is a text field in my table from which I don't want to get the full text, just first n chars. So if my query for example is:

Select description from articles where id='29';

Then how do I get the substring from description? thanks

解决方案

Use the substr function.

From the list of core functions:

substr(X,Y,Z)
substr(X,Y)

The substr(X,Y,Z) function returns a substring of input string X that begins with the Y-th character and which is Z characters long. If Z is omitted then substr(X,Y) returns all characters through the end of the string X beginning with the Y-th. The left-most character of X is number 1. If Y is negative then the first character of the substring is found by counting from the right rather than the left. If Z is negative then the abs(Z) characters preceding the Y-th character are returned. If X is a string then characters indices refer to actual UTF-8 characters. If X is a BLOB then the indices refer to bytes.

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