题目 : https://www.nowcoder.com/practice/642c34192f6345f0b365e71f69ced726?tpId=341
数据
drop table if exists deliver_record;
CREATE TABLE `deliver_record` (
`user_id` int NOT NULL,
`job_id` int NOT NULL,
`device` varchar(14) NOT NULL,
`job_salary` varchar(32) ,
`deliver_date` date NOT NULL
);
INSERT INTO deliver_record VALUES(101,14550, 'app','838900', '2020-03-01');
INSERT INTO deliver_record VALUES(102,14550, 'pc','67356','2021-07-07');
INSERT INTO deliver_record VALUES(103,23654, 'pc', null, '2021-04-09');
INSERT INTO deliver_record VALUES(102,23152, 'app','297032','2022-03-17');
INSERT INTO deliver_record VALUES(105,75432, 'pc','156770', '2006-08-15');
需求
查询所有用户 user_id , 并去重显示
结果显示 :
user_id
101
102
103
解决
利用 group by
进行去重
select user_id
from deliver_record
group by user_id;
利用 distinct
进行去重
select distinct(user_id)
from deliver_record;