从 sql 的结果中删除重复项

Question

i have following sql in java project:

select distinct * from drivers inner join licenses on  drivers.user_id=licenses.issuer_id
        inner join users on drivers.user_id=users.id 
        where (licenses.state='ISSUED' or drivers.status='WAITING')
        and users.is_deleted=false 

And result i database looks like this:

And i would like to get only one result instead of two duplicated results. How can i do that?

Answer 1

Solution 1 - That's Because one of data has duplicate value write distinct keyword with only column you want like this

Select distinct id, distinct  creation_date, distinct  modification_date from 
YourTable

Solution 2 - apply distinct only on ID and once you get id you can get all data using in query

select * from yourtable where id in (select distinct id from drivers inner join 
 licenses 
 on drivers.user_id=licenses.issuer_id
 inner join users on drivers.user_id=users.id 
 where (licenses.state='ISSUED' or drivers.status='WAITING')
 and users.is_deleted=false )

Answer 2

Enum fields name on select, using COALESCE for fields which value is null.

Answer 3

usually you dont query distinct with * (all columns), because it means if one column has the same value but the rest isn't, it will be treated as a different rows. so you have to distinct only the column you want to, then get the data

Answer 4

I suspect that you want left join s like this:

select *
from users u left join
     drivers d
     on d.user_id = u.id and d.status = 'WAITING' left join
     licenses l
     on d.user_id = l.issuer_id and l.state = 'ISSUED'
where u.is_deleted = false and
      (d.user_id is not null or l.issuer_id is not null);