如何使用MySQL在外键中插入值？

Question

我只有这两个表:

TAB_TEACHER
- id_teacher   // primary key, autoincrement
- name_teacher // a varchar

TAB_STUDENT
- id_student    // primary key, autoincrement
- name_student  // a varchar
- id_teacher_fk // foreign key reference to a teacher (TAB_TEACHER)

我想知道如何插入这两种情况:

案例1 - 使用预先存在的教师插入新学生,因此我必须使用教师姓名获取外键

案例2 - 使用新教师插入新学生(我正在创建学生的同时创建的老师)

Answer 1

http://dev.mysql.com/doc/refman/5.0/en/insert-select.html

对于case1:

INSERT INTO TAB_STUDENT(name_student, id_teacher_fk)
SELECT 'Joe The Student', id_teacher
  FROM TAB_TEACHER
 WHERE name_teacher = 'Professor Jack'
 LIMIT 1

对于case2,您只需要执行2个单独的插入语句

Answer 2

案例1:插入行和查询外键

这是我使用的替代语法:

INSERT INTO tab_student 
   SET name_student = 'Bobby Tables',
       id_teacher_fk = (
       SELECT id_teacher
         FROM tab_teacher
        WHERE name_teacher = 'Dr. Smith')

我在Excel中执行此操作以将数据透视表导入到维度表和SQL中的事实表,以便您可以从以下内容导入到bost department和expenses表:

情况2:插入行然后插入从属行

幸运的是,MySQL LAST_INSERT_ID()完全支持此目的.

INSERT INTO tab_teacher
   SET name_teacher = 'Dr. Smith';
INSERT INTO tab_student 
   SET name_student = 'Bobby Tables',
       id_teacher_fk = LAST_INSERT_ID()

Answer 3

情况1

INSERT INTO tab_student (name_student, id_teacher_fk)
    VALUES ('dan red', 
           (SELECT id_teacher FROM tab_teacher WHERE name_teacher ='jason bourne')

建议以小写形式存储您的值，以使检索更容易且不易出错

案例二

mysql 文档

INSERT INTO tab_teacher (name_teacher) 
    VALUES ('tom stills')
INSERT INTO tab_student (name_student, id_teacher_fk)
    VALUES ('rich man', LAST_INSERT_ID())