mysql查找最近的用户评论(第2部分)
续 同样,有两个表:mysql查找最近的用户评论(第2部分),mysql,Mysql,续 同样,有两个表: create table user( userID int auto_increment, userName varchar(10), userCreatedDate timestamp, primary key(userID) ); create table comment( commentID int auto-increment, userID int, comment varchar(100), primary key(commentID)
create table user(
userID int auto_increment,
userName varchar(10),
userCreatedDate timestamp,
primary key(userID)
);
create table comment(
commentID int auto-increment,
userID int,
comment varchar(100),
primary key(commentID),
foreign key(userID) references user(userID)
);
这次userCreateDate和commentID值与第1部分不同。我想从数据库中查找最近的评论。
我的输出如下:
以下是我尝试的查询:
select u.userID, max(c.commentID) as commentID, c.comment, u.userCreatedDate
from comment c
left join user u on c.userID = u.userID
group by u.userID
order by u.userCreateDate desc
然而,我无法获得我的输出有人能帮我吗?您可以按以下方式执行此操作,名为
分组最大/最小值
请尝试以下查询:-
select u.userID,commentID, c.comment, u.userCreatedDate
from comment c
left join user u on c.userID = u.userID
WHERE commentID=(SELECT MAX(c2.commentID)
FROM comment c2
WHERE c.userID = c2.userID)
select u.userID,commentID, c.comment, u.userCreatedDate
from comment c
left join user u on c.userID = u.userID
WHERE commentID=(SELECT MAX(c2.commentID)
FROM comment c2
WHERE c.userID = c2.userID)