MySQL通过比较两个以上的列从两个不同的表中选择匹配和不匹配的记录

Question

system Table

id sys_id  sys_date  sys_load
-- ------ ---------- --------
1   4472  2017-09-06  500000
2   5678  2017-09-06  300000
3   4323  2017-09-06  400000
4   8976  2017-09-06  200000
5   8976  2017-09-06  0
6   9890  2017-09-06  0
7   9890  2017-09-06  100000
8   9999  2017-09-06  200000
9   4472  2017-09-05  100000
10  5678  2017-09-05  900000

man Table

id man_id  man_date  man_load
-- ------ ---------- --------
1   4472  2017-09-06  500000
2   5678  2017-09-06  300000
3   4323  2017-09-06  400000
4   8976  2017-09-06  200000
5   9890  2017-09-06  100000

1.I want to select records from system table by matching sys_id,sys_date,sys_load with man table man_id,man_date,man_load. date comes from front end.

select sys_id
     , sys_load 
  from system
     , man 
 where DATE(sys_date) = '2017-09-06' 
   and man_date = '2017-09-06' 
   and sys_id = man_id 
   and sys_load = man_load_amt 
 order 
    by sys_id; 

gives me the expected result like below

1   4472  2017-09-06  500000
2   5678  2017-09-06  300000
3   4323  2017-09-06  400000
4   8976  2017-09-06  200000
5   9890  2017-09-06  100000

is the above query is good or any wrong in it?

2.Now i want to select the records from system table which are not matching with the above result set for the date '2017-09-06'. ie,

id sys_id  sys_date  sys_load
-- ------ ---------- --------
5   8976  2017-09-06  0
6   9890  2017-09-06  0
8   9999  2017-09-06  200000

note: ids 8976 and 9890 have two entries. any help would be really appreciated.

Answer 1

Please get rid of old styled joins. Please use explicit join syntax -

1 - For matching records

select sys_id
      ,sys_load 
from system
inner join man on sys_id = man_id 
where DATE(sys_date) = '2017-09-06' 
and man_date = '2017-09-06' 
and sys_load = man_load_amt 
order by sys_id;`

Edit - I have just noticed you have unmatched records in system also. So you need left join rather than inner

2 - For un-matching records

select sys_id
      ,sys_load 
from system
left join man on sys_id = man_id 
where DATE(sys_date) = '2017-09-06' 
and (sys_load <> man_load or man_load is null)
order by sys_id;