Mysql复制错误

Question

为了在表(“projects”)中插入唯一的“project_title”值，我编写了如下查询。

INSERT INTO projects (projects.project_title, projects.description) 
SELECT * FROM (SELECT 'a title', 'a description') AS tmp 
WHERE NOT EXISTS (SELECT projects.project_title FROM projects WHERE projects.project_title = 'a title') LIMIT 1

这工作正常，直到为项目标题和项目描述输入相同的条目并且查询将如下所示:

INSERT INTO projects (projects.project_title, projects.description) 
SELECT * FROM (SELECT 'text', 'text') AS tmp 
WHERE NOT EXISTS (SELECT projects.project_title FROM projects WHERE projects.project_title = 'text') LIMIT 1

现在，我得到这个错误:

[Err] 1060 - Duplicate column name 'text'

如何摆脱这个重复错误？!

Answer 1

在此处提取错误语句:

SELECT 
 tmp.*
FROM 
(
    SELECT 'text', 'text'
) AS tmp;

这个查询会产生这个错误

[Err] 1060 - Duplicate column name 'text'

因为您没有为列指定任何别名。

解决方案:

给列起别名:

SELECT 
  tmp.*
FROM 
(
    SELECT 
      'text' AS firstText, 
      'text' AS secondText
) AS tmp;