database - 如何在 SQLIte 中获取子字符串？

Question

我从 SQLite 数据库中检索了很多数据。检索时，我将其映射到应用程序中的不同 View 。我的表中有一个文本字段，我不想从中获取全文，只是前 n 个字符。因此，如果我的查询是:

Select description from articles where id='29';

那么如何从描述中获取子字符串呢？谢谢

Answer 1

使用 substr 函数。

来自list of core functions :

substr(X,Y,Z) substr(X,Y) substring(X,Y,Z) substring(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.

substring() is an alias for substr() beginning with SQLite version 3.34.