mysql在同一表记录中的2行比较

Question

我已经搜索了网角转角，但还没有找到我的问题的解决方案。我有一张名为master的表，其中包含有问题的设备记录。当设备首次记录在数据库中时，作业的状态为cat_id = 11，当有人修复它时，他们再次输入相同的信息并将状态更改为cat_id = 1或2或3等。当cat_id（status）变成别的东西然后cat_id = 11我想用这个“mo_number”和cat_id =别的东西来做这个工作，不要在select查询中出现。

表：主

id mo_number part_number cat_id  date_created user_id 
15 7200023   347893  11  01/03/2016  1 
33 7200023   347893  1  10/03/2016  5 
34 7200045   457890  11  11/03/2016  1 

expected : 
id mo_number part_number cat_id  date_created user_id 
34 7200045   457890  11  11/03/2016  1 

这里是我的完整选择查询：

SELECT m.comment_id, m.mo_number, m.part_number, m.serial_number, m.comment, 
     m.date_created, CONCAT(u.first_name, ' ', u.last_name) as name 
     FROM master AS m 
     INNER JOIN users as u ON u.user_id = m.user_id 
      INNER JOIN category as c ON m.cat_id = c.cat_id 
     WHERE u.user_id = '1' AND m.cat_id = '11' 
    ORDER BY m.mo_number DESC 

我不知道怎么写查询，以便这项工作并不在表中显示出来还开着。如果有人能帮忙，我将不胜感激。

Answer 1

SQL Fiddle

的MySQL 5.5架构设置：

create table users (user_id int, first_name varchar(100), last_name nvarchar(100)); 
insert users (user_id, first_name, last_name) 
select 1, 'John', 'Smith' 
union 
select 5, 'Neo', 'Anderson' 
; 

create table category (cat_id int, name varchar(100)); 
insert category (cat_id, name) 
select 1, 'closed' 
union 
select 2, 'not so closed but not open too :)' 
union 
select 11, 'open' 
; 

create table master (
    id int, mo_number varchar(10), part_number varchar(10), serial_number varchar(10), 
    cat_id int, date_created date, user_id int, comment varchar(100)); 

insert master (id, mo_number, part_number, serial_number, cat_id, date_created, user_id, comment) 
select 15, '7200023', '347893', 'SN00001', 11, '2016-03-01', 1, 'seems we can do it' 
union 
select 33, '7200023', '347893', 'SN00001', 1, '2016-03-10', 5, 'tested by Morpheus' 
union 
select 34, '7200045', '457890', 'SN00002', 11, '2016-03-11', 1, 'again that Miss drop it to bath ' 

查询1：

SELECT m.mo_number, m.part_number, m.serial_number, m.comment, 
    m.date_created, CONCAT(u.first_name, ' ', u.last_name) as name 
FROM master AS m 
    INNER JOIN users as u ON u.user_id = m.user_id 
    INNER JOIN category as c ON m.cat_id = c.cat_id 
WHERE m.cat_id = 11 and not exists(
    select 1 from master as m1 
    where m1.cat_id <> 11 
    and m1.date_created > m.date_created 
    and m1.mo_number = m.mo_number) 
ORDER BY m.mo_number DESC 

Results：

| mo_number | part_number | serial_number |       comment |   date_created |  name | 
|-----------|-------------|---------------|----------------------------------|-------------------------|------------| 
| 7200045 |  457890 |  SN00002 | again that Miss drop it to bath | March, 11 2016 00:00:00 | John Smith |