从字符串中获取第一个字符 [英] Get first characters from a String

问题描述

我有一个包含 30 个字符的字符串，但我只需要其中的 20 个.我怎样才能获得前 20 个?

I have a string with 30 characters but i only need the 20 of them. How can i get the first 20?

我试过这个子串(ltrim(rtrim(field_value)),20)

I tried this substring(ltrim(rtrim(field_value)),20)

但是没有用.有什么想法吗?

But didn't work. Any ideas?

推荐答案

在My SQL中，您可以使用LEFT(或SUBSTRING)从一个 string.由于您需要的是第一个字符，我建议使用 LEFT:

In My SQL, you could use LEFT (or SUBSTRING) to SELECT certain number of characters from a string. Since what you need is the first characters, I suggest to use LEFT:

SELECT LEFT(field_value, 20) FROM MyTableName

原文:

(由于标签原本是C#，下面的解决方案提供了C#问题的解决方案)

(As the tag was originally C#, the following solution below provides solution for C# problem)

您应该使用 Substring(0, 20).第一个参数 (0) 是起始索引，第二个参数 (20) 是您想要获取的 string 的长度.

You should use Substring(0, 20). The first argument (0) is the starting index, and the second argument (20) is the length of the string you want to take.

例如:

var str = "123456789012345678901234567890";
str = str.Substring(0, 20);

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