MySQL查询 - 显示效果都没有另一个表

Question

我有这样的查询：

SELECT lesson.id, p1.first_name, p1.surname, start_time, instrument.name 
FROM lesson, person AS p1, person AS p2, instrument, invoice_lesson 
WHERE lesson.student = p1.id 
AND lesson.teacher = p2.id 
AND instrument.id = lesson.instrument_id 
ORDER BY surname 

不过，我想修改它，使它只显示结果，其中lesson.id不在表invoice_lesson.lesson_id 。这是一个相关的查询吗？我该怎么做呢？

Answer 1

你可以用外做加盟：

SELECT lesson.id, p1.first_name, p1.surname, start_time, instrument.name 
FROM lesson l JOIN person p1 ON l.student = p1.id 
JOIN person p2 ON l.teacher = p2.id 
JOIN instrument i ON i.id = l.instrument_id 
LEFT JOIN invoice_lesson il ON l.id = il.lesson_id 
WHERE il.lesson_id IS NULL 
ORDER BY surname 

这种方法将比相关的子查询方法快得多。

Answer 2

最简单的方法：

SELECT lesson.id, p1.first_name, p1.surname, start_time, instrument.name 
FROM lesson, person AS p1, person AS p2, instrument, invoice_lesson 
WHERE lesson.student = p1.id 
AND lesson.teacher = p2.id 
AND instrument.id = lesson.instrument_id 
AND lesson.id NOT IN (SELECT lesson_id FROM invoice_lesson) 
ORDER BY surname 

也许不完全是最快的:)

托马斯Kopczuk

Answer 3

尝试使用JOIN：

SELECT lesson.id, p1.first_name, p1.surname, start_time, instrument.name 
FROM lesson, person AS p1, person AS p2, instrument, invoice_lesson 
JOIN invoice_lesson 
ON lession.id = invoice_lession.lesson_id 
WHERE lesson.student = p1.id 
AND lesson.teacher = p2.id 
AND instrument.id = lesson.instrument_id 
ORDER BY surname