如何從字段mysql中的前20個字符后選擇字符

Question

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

如何在20個字符后選擇字符串？

Answer 1

要獲取前20個字符之后的字符（請注意，如果沒有20個字符，該函數將返回一個空字符串）：

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

現在，如果您需要地址2為NULL，則首先檢查字符長度：

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

要獲取前20個字符，可以使用子字符串函數，如下所示：

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

現在最終的查詢可能如下所示：

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

Answer 2

substring是您要查找的內容：

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