如何从字段mysql中选择前20个字符后的字符答案

【问题标题】：how to select characters after first 20 characters from field mysql如何从字段mysql中选择前20个字符后的字符
【发布时间】：2014-12-13 10:01:24
【问题描述】：

 select address (first 20 character) as Address1 , 
        address (characters after first 20 if less then 20 then NULL) as Address2
 from customer

如何选择 20 个字符后的字符串？

【问题讨论】：

【解决方案1】：

获取前 20 个字符之后的字符（注意如果没有 20 个字符，函数将返回一个空字符串）：

SELECT SUBSTRING('Some Random Address That is Longer than 20 characters' FROM 20);

现在如果你需要地址 2 为 NULL，你首先检查字符长度：

SELECT if(char_length(address) > 20, SUBSTRING(address FROM 20), NULL);

要获取前 20 个字符，可以像这样使用 substring 函数：

SELECT SUBSTRING('Some Random Address', 1, 20);

现在最终的查询可能如下所示：

SELECT SUBSTRING(address, 1, 20) as Address1, 
    IF(CHAR_LENGTH(address) > 20, SUBSTRING(address FROM 20), NULL) as Address2
FROM customer

【讨论】：

【解决方案2】：

substring 是您正在寻找的：

SELECT SUBSTRING(address, 1, 20) AS Address1, 
       SUBSTRING(address FROM 20) AS Address2
FROM   customer

【讨论】：