Question

假设我在sql中有以下表格。

student 
name   id
alex   1
felix  2
hannah 3
john   4 
jonas  5


instructor  
name   id
alex   1
felix  2
hannah 3
john   4 
jonas  5
(ex)brad   8
tom    9
tonny  11

instructor_lectures
name   id   course_count
alex   1    5
felix  2    2
hannah 3    0
john   4    23
jonas  5    12
(ex)brad   8    1
tom    9    11
tonny  11   9

我想做的是;

- firstly, get the difference of instructor student tables according to the name which does not start with "(ex)"
- and then list course_count of the result.

我的意思是，先得到

name   id
tom    9
tonny  11

然后

name   id   course_count
tom    9    11
tonny  11   9

到目前为止我做了什么？

我已经编写了差异查询并从instructor_lectures中选择查询，但无法将它们组合在一起。

SELECT NAME FROM instructor INSTR WHERE NOT EXISTS 
(
    SELECT * FROM student STU WHER INSTR.NAME = STU.NAME
) 
AND INSTR.NAME NOT REGEXP '^(ex)'

此查询返回

name   id
tom    9
tonny  11

现在我想通过查看table instructor_lectures

来获取course_count

SELECT NAME FROM instructor INSTR WHERE NOT EXISTS 
(
    SELECT * FROM student STU WHER INSTR.NAME = STU.NAME
) 
AND INSTR.NAME NOT REGEXP '^(ex)'
SELECT * FROM instructor_lectures INSTR_LECTURES WHERE INSTR.NAME = INSTR_LECTURES.NAME

但这会引发错误。我的错误在哪里？如何获取第一个差异查询结果的course_count？

Answer 1

SELECT INSTR.NAME, INSTR.id, INSTR_LECTURES.COURSE_COUNT
  FROM instructor INSTR, instructor_lectures INSTR_LECTURES
 WHERE NOT EXISTS (SELECT * FROM student STU WHER INSTR.NAME = STU.NAME)
   AND INSTR.NAME NOT REGEXP '^(ex)'
   and INSTR.NAME = INSTR_LECTURES.NAME

使用加入条件，了解joins

上的信息

无法在sql中创建链查询

1 个答案: