带有子查询的INSERT查询：列数与第1行的值数不匹配

Question

我有这样的查询，它使用子查询插入行：

INSERT INTO Lecture_presence_Student (`presence_id`, `Lecture_id`, `Student_id`, `status`) VALUES

(
 (
  SELECT '' as presence_id, Lecture.Lecture_id, CourseEdition_students_Student.Student_id, 'onverwerkt' 
  FROM
    CourseEdition_students_Student 
        INNER JOIN Lecture ON    CourseEdition_students_Student.CourseEdition_id = Lecture.CourseEdition_id



    )       
)

我不明白，子选择查询返回4列，与INSERT查询的编号相同。为什么会出现错误：

Column count doesn't match value count at row 1

有任何想法吗？

Answer 1

代替INSERT INTO VALUES使用INSERT INTO SELECT FROM

INSERT INTO Lecture_presence_Student 
(
    `presence_id`
    , `Lecture_id`
    , `Student_id`
    , `status`
) 
SELECT '' as presence_id
    , Lecture.Lecture_id
    , CourseEdition_students_Student.Student_id
    , 'onverwerkt' 
FROM    CourseEdition_students_Student 
INNER JOIN Lecture 
    ON    CourseEdition_students_Student.CourseEdition_id = Lecture.CourseEdition_id

那么如果您在查询中获得多个记录，则该记录INSERT将起作用。