在同一個sql語句中使用mysql別名

Question

如何在同一個語句中使用別名？在下面的語句中查看body別名。當我和（長（機構）使用它，我得到unknown column。

SELECT substring_index(userBody, ' ', 60) as body, SUM(LENGTH(body)-LENGTH(REPLACE(body,' ',''))+1) as wordCount 
from articles where artcId = 10; 

Answer 1

在未來選擇列不能使用body別名，更好地使用相同的「別名」塊在下面的章節。請參見下面的查詢更多的澄清。

SELECT substring_index(userBody, ' ', 60) as body, SUM(LENGTH(substring_index(userBody, ' ', 60))-LENGTH(REPLACE(substring_index(userBody, ' ', 60),' ',''))+1) as wordCount from articles where artcId = 10; 

Answer 2

不能使用別名列名detch數據anothe列。

您可以使用子查詢或採用S對於另一列AME功能如下解釋：

使用子查詢

SELECT body, SUM(LENGTH(body)-LENGTH(REPLACE(body,' ',''))+1) AS wordCount 
FROM (SELECT SUBSTRING_INDEX(userBody, ' ', 60) AS body 
     FROM articles WHERE artcId = 10) AS A 

或使用同一功能

SELECT SUBSTRING_INDEX(userBody, ' ', 60) AS body, 
     SUM(LENGTH(SUBSTRING_INDEX(userBody, ' ', 60))-LENGTH(REPLACE(SUBSTRING_INDEX(userBody, ' ', 60),' ',''))+1) AS wordCount 
FROM articles WHERE artcId = 10; 

Answer 3

你不能。或者，您可以使用子查詢，例如。

SELECT body, 
     SUM(LENGTH(body)-LENGTH(REPLACE(body,' ',''))+1) as wordCount 
FROM 
    (
     SELECT substring_index(userBody, ' ', 60) as body 
     from articles 
     where artcId = 10 
    ) s