MySQL CONCAT 找不到带有别名的 table

Question

我有一个相当直接的查询，我不明白为什么 CONCAT 不起作用。

我是 JOINING 表 domains client_content 和 domain_status 并试图 insert into vhosts。在我使用 CONCAT 组合 domain_status.status_directory 和 client_configuration.user_file 之前，所有工作都按预期进行。此时我分配的别名是否超出范围？

                      ----------------------------------------
domains               |  domain   |   enabled   |   status   |
                      ----------------------------------------

                      -------------------------------------
client_configuration  |   contractor_id   |   user_file   |
                      -------------------------------------

                      ---------------------------------
domain_status         |   id   |   status_directory   |
                      ---------------------------------

                      ------------------------------------------------------------
vhosts                |   site_name   |   directory   |   enabled   |   status   |
                      ------------------------------------------------------------


INSERT INTO vhosts (`site_name`, `directory`, `enabled`, `status`)
    SELECT d.domain, CONCAT(`s.status_directory`,'/',`c.user_file`), d.enabled, d.status  
    FROM domains d

    LEFT JOIN client_configuration c
        ON d.contractor_id = c.contractor_id
    LEFT JOIN domains_status s
        ON d.status = s.id
    WHERE d.domain = 'example.com';

据我了解，我应该能够以这种方式使用 CONCAT，但我收到 MySQL 错误：

Error Code: 1054. Unknown column 's.status_directory' in 'field list'

如果我不能像这样使用 CONCAT .. 有什么解决方法？

Answer 1

问题是您用与列名相同的反引号将 table 别名括起来。从这些引号中取出 table 别名。试试这个：

INSERT INTO vhosts 
(
  `site_name`, 
  `directory`, 
  `enabled`, 
  `status`
)
SELECT 
  d.domain, 
  CONCAT(s.`status_directory`,'/', c.`user_file`), 
  d.enabled, 
  d.status  
FROM domains d
LEFT JOIN client_configuration c
  ON d.contractor_id = c.contractor_id
LEFT JOIN domains_status s
  ON d.status = s.id
WHERE d.domain = 'example.com';

Answer 2

删除引号：INSERT INTO vhosts (site_name, directory, enabled, status) SELECT d.domain, CONCAT(s.status_directory,'/',c.user_file) as statusUserFile, d.enabled, d.status FROM domains d LEFT JOIN client_configuration c ON d.contractor_id = c.contractor_id LEFT JOIN domains_status s ON d.status = s.id WHERE d.domain = 'example.com';

MySQL CONCAT 找不到带有别名的 table

MySQL CONCAT not finding table with alias

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concatenation