使用 CTE 的 SQL 错误

Question

我收到此错误：

查询错误：您的 SQL 语法有错误；检查与您的 MariaDB 服务器版本相对应的手册，以了解在 ';WITH convs AS ( select c.id, c.title, c.seen, c.id_receiver, c.id_send' at line 1 附近使用的正确语法

当我使用这个查询时：

$query = ";WITH convs AS (
        select c.id, c.title, c.seen, c.id_receiver, c.id_sender
        from conversations c
        )
        select id, title, seen, id_receiver, id_sender
        from convs
        where id_receiver = '5'
        order by title desc limit 0,25";

$res = mysqli_query($connection ,$query);

我错过了什么吗？ 非常感谢您的帮助。

PS：我最小化了查询以使其在此上下文中变得简单，如果您帮助我找到解决方案，我可能对完整查询有另一个问题。所以我可能会回来找你寻求更多帮助。提前致谢。

编辑（整个查询）

$query = "WITH convs AS (
        select c.id, c.title, c.seen, c.id_receiver, c.id_sender,
        (select max(date) from messages where id_conversation = c.id and id_user <> '$iduser') as last_msg,
        (select top 1 id_user from messages where id_conversation = c.id and id_user <> '$iduser' order by date desc) as last_user,
        (select count(distinct id_user) from messages where id_conversation = c.id) as nbruser,
        (select count(*) from messages where id_conversation = c.id) as nbrmsg,
        (select username from users where id = c.id_sender) as sender, (select username from users where id = c.id_receiver) as receiver,
        (select count(*) from deleted_conversations where id_user='$iduser' and id_conversation=c.id) as deleted,
        from conversations c
        )
        select id, title, seen, id_receiver, id_sender, receiver, sender, last_msg, last_user, deleted, nbruser, nbrmsg
        from convs
        where (id_receiver = '$iduser' or (id_sender == '$iduser' and nbruser > 1)) and deleted = 0
        order by last_msg desc limit $pageLimit,$REC_PER_PAGE";

促使我使用 CTE 的原因是需要在 where 子句中使用别名。正如你所看到的，我有很多。

你能举个例子说明如何使用视图/临时表来实现我的目的吗？

Answer 1

MySQL/MariaDB 不支持 CTE。另外，在这种情况下完全没有必要：

    select id, title, seen, id_receiver, id_sender
    from conversations c
    where id_receiver = '5'
    order by ?? desc
    limit 0, 25;

注意：您还需要为order by 指定列。

对于更复杂的示例，您可以使用子查询、视图和/或临时表。

Answer 2

CTE 与派生表非常相似：

select id, title, seen, id_receiver, id_sender, receiver, sender, last_msg, last_user, deleted, nbruser, nbrmsg
FROM
 (
        select c.id, c.title, c.seen, c.id_receiver, c.id_sender,
        (select max(date) from messages where id_conversation = c.id and id_user <> '$iduser') as last_msg,
        (select top 1 id_user from messages where id_conversation = c.id and id_user <> '$iduser' order by date desc) as last_user,
        (select count(distinct id_user) from messages where id_conversation = c.id) as nbruser,
        (select count(*) from messages where id_conversation = c.id) as nbrmsg,
        (select username from users where id = c.id_sender) as sender, (select username from users where id = c.id_receiver) as receiver,
        (select count(*) from deleted_conversations where id_user='$iduser' and id_conversation=c.id) as deleted,
        from conversations c
) as convs
where (id_receiver = '$iduser' or (id_sender == '$iduser' and nbruser > 1)) and deleted = 0
order by last_msg desc limit $pageLimit,$REC_PER_PAGE