MySQL：查询优化 - 如何将查询结果存储在变量中

Question

我有表用户、活动（公共、私人或秘密类型）、服务员、组织者，我需要选择用户 1 是服务员或组织者的所有活动，除了秘密活动，其中用户 2 不是（参加或组织者或受邀）。

这个巨大的 SELECT 可以满足我的所有需要​​，但它包含许多其他 SELECT。 是否可以以某种方式对其进行优化，例如将由 cmets 从这里到这里的联合体放入某种变量并重新使用它？

编辑：当时我需要能够处理更多这些请求。

SELECT `event`.id AS eventid, event.name AS ename
FROM attendant
INNER JOIN user ON attendant.fk_user = user.id
INNER JOIN event ON attendant.fk_event = `event`.id
WHERE user.id = 2
AND attendant.fk_event = `event`.id
AND `event`.id IN
-- FROM HERE
(
SELECT `event`.id
FROM attendant
INNER JOIN user ON attendant.fk_user = user.id
INNER JOIN event ON attendant.fk_event = `event`.id
WHERE user.id = 1
AND attendant.fk_event = `event`.id

UNION

SELECT `event`.id
FROM organizer
INNER JOIN user ON organizer.fk_user = user.id
INNER JOIN event ON organizer.fk_event = event.id
WHERE user.id = 1
AND organizer.fk_event = event.id

UNION

SELECT `event`.id
FROM invitation
INNER JOIN user ON invitation.fk_user_to = user.id
INNER JOIN event ON invitation.fk_event = event.id
WHERE invitation.fk_user_to = 1
AND invitation.fk_event = event.id)
-- TO HERE

UNION

SELECT `event`.id AS eventid, event.name AS ename
FROM organizer
INNER JOIN user ON organizer.fk_user = user.id
INNER JOIN event ON organizer.fk_event = event.id
WHERE user.id = 2
AND organizer.fk_event = event.id
AND `event`.id IN
(
-- FROM HERE
SELECT `event`.id
FROM attendant
INNER JOIN user ON attendant.fk_user = user.id
INNER JOIN event ON attendant.fk_event = `event`.id
WHERE user.id = 1
AND attendant.fk_event = `event`.id

UNION

SELECT `event`.id
FROM organizer
INNER JOIN user ON organizer.fk_user = user.id
INNER JOIN event ON organizer.fk_event = event.id
WHERE user.id = 1
AND organizer.fk_event = event.id

UNION

SELECT `event`.id
FROM invitation
INNER JOIN user ON invitation.fk_user_to = user.id
INNER JOIN event ON invitation.fk_event = event.id
WHERE invitation.fk_user_to = 1
AND invitation.fk_event = event.id);
-- TO HERE

Answer 1

我建议创建视图以获取中间结果并重用它们。

视图很便宜：数据不存储，您可以在选择中使用它们。

以你为例：

create view viewname_1 as SELECT event.id FROM invitation INNER JOIN user ON invitation.fk_user_to = user.id INNER JOIN event ON invitation.fk_event = event.id WHERE invitation.fk_user_to = 1 AND invitation.fk_event = event.id AND (event.type = 'secret' OR event.type = 'private' OR event.type = 'public') )`

以后使用 viewname_1 作为 select * from viewname_1...

显然，您可以为视图选择自己的命名约定：只需注意命名空间。