mysql插入多个选择语句

Question

I want to insert data to a table with values coming from 3 different tables

table class_teachers_section
class_ref teachers_ref section_ref
2 3 2 1 6 2

table class id name hours 1 pe 3

table teachers id first_name last_name 1 Lenovo Lenovo

table section id name 1 grade 4

class_teachers_section is a intermediary table ... here is my statement

INSERT INTO class_teachers_section(class_ref, teachers_ref, section_ref)
    values (
        (class_ref, (select class.id as class_ref from class where class.name = 'pe')),
        (teachers_ref, (select teachers.id as teachers_ref from teachers where
                    teachers.last_name = 'lenevo')),
        (section_ref, (select section.id as section_ref from section where section.name =
                   'grade 4'))
    )

1241 - Operand should contain 1 column(s)

do you guys have any idea how to resolve this? thanks

tried this ..

INSERT INTO class_teachers_section(class_ref, teachers_ref, section_ref)
    values( (select class.id as class_ref from class where class.name = 'pe'),
           (select teachers.id as teachers_ref from teachers where teachers.last_name = 'lenevo'),
           (select section.id as section_ref from section where section.name = 'grade 4'))

teachers_ref can not be null error

Answer 1

Your syntax is rather unusual. You have three columns in the insert list but have six elements in the values list. Three of them appear to be column names.

That is not how select works. Instead, the columns correspond by position.

In your case, though, you should use insert . . . select insert . . . select insert . . . select :

INSERT INTO class_teachers_section(class_ref, teachers_ref, section_ref)
    select (select class.id as class_ref from class where class.name = 'pe'),
           (select teachers.id as teachers_ref from teachers where teachers.last_name = 'lenevo'),
           (select section.id as section_ref from section where section.name = 'grade 4');