mysql查询-怎么判断一个用户在多个表中是否有值

Question

场景如下，
有一张用户表user，主键用户编号user_id ，类型int; 三张业务表 a_record，b_record，c_record，分别都含有外键user_id.

在方法中，别人传给我一串user_id ，字符串的，逗号分割的，如“1001,2001,2003,98”；
我需要去数据库中判断这些user_id串中的用户是否有三种业务中至少一条的记录，
（只要这个user_id字符串中的有一个人有其中之一业务记录，我就可以返回true，否则返回false ）

这个sql语句怎么写？

Answer 1

select num(user,id) from user,a_record where user_id = a_record
union
select num(user,id) from user,a_record where user_id = b_record
union
select num(user,id) from user,a_record where user_id = c_record

Answer 2

select count(1) from user u,a_record a,b_record b,c_record c where u.user_id=a.user_id and u.user_id=b.user_id and u.user_id=c.user_id

Answer 3

select count(*) from user u,a_record a，b_record b，c_record c
when u.user_id=a.user_id or u.user_id=b.user_id or u.user_id=c.user_id

Answer 4

如果user中 的user_id 是字符串的，如“1001,2001,2003,98”：
select count(*) from user u,a_record a，b_record b，c_record c
when a.user_id in (u.user_id) or a.user_id in (u.user_id) or a.user_id in (u.user_id)

Answer 5

select user,id from user,a_record where user_id in(1000,1001,1002)
union
select user,id from user,a_record where user_id in (1000,1001,1002)
union
select user,id from user,a_record where user_id in (1000,1001,1002)