Question

正如标题所说，我可以在 MySQL 中预定义一些结果集（因为它是从内层到外层进行评估），稍后在查询中重用它们吗？

我在这里有一个示例查询（不要被大小吓到）：

SELECT id, globalId, date, serverId, gamemodeId, mapId FROM
        (
            (SELECT * FROM
            (
                SELECT
                ll.id AS id, ll.globalId AS globalId, ll.date AS date, ll.serverId AS serverId, ll.gamemodeId AS gamemodeId, ll.mapId AS mapId, origin
                FROM
                (
                        (SELECT id, globalId, date, serverId, playerId, 'playerjoins' AS origin
                        FROM playerjoins pj
                        WHERE playerId = 976)
                    UNION ALL
                        (SELECT id, globalId, date, serverId, playerId, 'playerleaves' AS origin
                        FROM playerleaves pl
                        WHERE playerId = 976)
                    ORDER BY date DESC
                ) pjl
                JOIN levelsloaded ll
                ON pjl.date <= ll.date
                GROUP BY ll.id
                ORDER BY ll.date DESC
            ) above
            WHERE origin = 'playerjoins')
        UNION ALL
            (SELECT * FROM
                (
                    SELECT
                    ll.id AS id, ll.globalId AS globalId, ll.date AS date, ll.serverId AS serverId, ll.gamemodeId AS gamemodeId, ll.mapId AS mapId, origin
                    FROM
                    (
                            (SELECT id, globalId, date, serverId, playerId, 'playerjoins' AS origin
                            FROM playerjoins pj
                            WHERE playerId = 976)
                        UNION ALL
                            (SELECT id, globalId, date, serverId, playerId, 'playerleaves' AS origin
                            FROM playerleaves pl
                            WHERE playerId = 976)
                        ORDER BY date DESC
                    ) pjl
                    JOIN levelsloaded ll
                    ON pjl.date >= ll.date
                    GROUP BY ll.id
                    ORDER BY ll.date DESC
                ) below
            WHERE origin = 'playerleaves')
        ) total
        ORDER BY date DESC

我想以某种方式预定义pjl：

            (
                    (SELECT id, globalId, date, serverId, playerId, 'playerjoins' AS origin
                    FROM playerjoins pj
                    WHERE playerId = 976)
                UNION ALL
                    (SELECT id, globalId, date, serverId, playerId, 'playerleaves' AS origin
                    FROM playerleaves pl
                    WHERE playerId = 976)
                ORDER BY date DESC
            ) pjl

我在完整查询中使用了两次。我在查询开始时想象一下 pjl = (...)，然后在其余代码中，您可以使用pjl。它应该仅在查询的生命周期内有效。

如果在PHP / MySQL设置中使用多行查询（使用;）定义，我可以看到发生的一些问题。

Answer 1

您可以使用MySQL中的过程（或可能是函数）来完成此操作：http://dev.mysql.com/doc/refman/5.1/en/create-procedure.html或http://dev.mysql.com/doc/refman/5.1/en/stored-routines.html

是否可以在MySQL中预定义查询？

1 个答案: