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cosito
Asked: 2020-02-18 21:13:22 +0800 CST 2020-02-18 21:13:22 +0800 CST

What does a select in an insert mean and do?

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I have this statement, but my question is what does select 1 do, and how would it look, some example, that you could provide me with an explanation.

 insert into grades (idStudent,idCourse)   
    select 1, id from courses where idGroup=groupId;
mysql

1 Answers

  1. Best Answer

    It will perform an insert into the table gradeswhere the match idGroup=groupId;is true.

    That is, if your table gradeslooks like this

    idStudent,idCourse

    So when performing the query

    insert into grades (idStudent,idCourse)   
    select 1, id from courses where idGroup=groupId;

    The table should look like this

    idStudent,idCourse
    1         20

    Understanding that it 20is an example value that you can take given the query and its last condition.

    In summary

    The columns idStudentand idCoursewill be filled with the number 1as a constant value for the first column and for the second column with the value that results after the conditionwhere idGroup=groupId;

    The column idCoursein the table gradesis to be populated specifically with the table columncourses

    All of the above provided that said condition, as I already said, is met

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