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Question

这是sqlFiddle，显示了我想要做的事情这是@ lad2025 sqlFiddle更好地展示了

我的桌子上有两个索引，还有一个包含列名的列和一个包含值的列。

在小提琴中，我展示了一个执行我想要做的事情的查询。但它很慢。

我有一个交叉表请求几乎完全相同，非常快，但错误很少。（它会融合一些线条）

SELECT 
    end_user_id, 
    tms, 
    coalesce(max(IN_VEHICLE), 0) as IN_VEHICLE, 
    coalesce(max(ON_BICYCLE), 0) as ON_BICYCLE, 
    coalesce(max(ON_FOOT),    0) as ON_FOOT, 
    coalesce(max(RUNNING),    0) as RUNNING, 
    coalesce(max(STILL),      0) as STILL, 
    coalesce(max(TILTING),    0) as TILTING, 
    coalesce(max(UNKNOWN),    0) as UNKNOWN, 
    coalesce(max(WALKING),    0) as WALKING 
FROM
    crosstab (            
        'SELECT end_user_id, tms, type, max(confidence) FROM activities group by 1,2,3 ',
        'SELECT DISTINCT type FROM activities order by type'
    )as newtable (
        end_user_id text, 
        tms         timestamp,
        IN_VEHICLE  float,
        ON_BICYCLE  float,
        ON_FOOT     float,
        RUNNING     float,
        STILL       float,
        TILTING     float,
        UNKNOWN     float,
        WALKING     float
    )  
GROUP BY end_user_id, tms
ORDER BY end_user_id, tms

我不知道为什么postgres要求我使用GROUP BY end_user_id，最后是tms ...它应该是唯一的。
我也不知道为什么，但如果我不在交叉表查询中分组，我每个end_user_id只有一行：（

如何更正该交叉表请求？

修改： @ lad2025响应是一个比我更好的例子，更优雅，我肯定更快。不过，我想知道如何使用交叉表进行操作。

Answer 1

您可以在Fiddle中避免使用交叉表/多重左连接，并使用简单的条件聚合：

SELECT 
 end_user_id,
 tms,
 COALESCE(MAX(CASE WHEN type = 'IN_VEHICLE' THEN confidence END),0) AS IN_VEHICLE,
 COALESCE(MAX(CASE WHEN type = 'ON_BICYCLE' THEN confidence END),0) AS ON_BICYCLE,
 COALESCE(MAX(CASE WHEN type = 'ON_FOOT'    THEN confidence END),0) AS ON_FOOT,
 COALESCE(MAX(CASE WHEN type = 'RUNNING'    THEN confidence END),0) AS RUNNING,
 COALESCE(MAX(CASE WHEN type = 'STILL'      THEN confidence END),0) AS STILL,
 COALESCE(MAX(CASE WHEN type = 'TILTING'    THEN confidence END),0) AS TILTING,
 COALESCE(MAX(CASE WHEN type = 'UNKNOWN'    THEN confidence END),0) AS UNKNOWN,
 COALESCE(MAX(CASE WHEN type = 'WALKING'    THEN confidence END),0) AS WALKING
FROM activities
GROUP BY end_user_id, tms
ORDER BY end_user_id, tms;

的 SqlFiddleDemo

输出：

╔═══════════════════╦════════════════════════════╦═════════════╦═════════════╦══════════╦══════════╦════════╦══════════╦══════════╦═════════╗ ║ end_user_id ║ tms ║ in_vehicle ║ on_bicycle ║ on_foot ║ running ║ still ║ tilting ║ unknown ║ walking ║ ╠═══════════════════╬════════════════════════════╬═════════════╬═════════════╬══════════╬══════════╬════════╬══════════╬══════════╬═════════╣ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:24:20 ║ 21 ║ 8 ║ 2 ║ 0 ║ 2 ║ 0 ║ 68 ║ 2 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:24:41 ║ 15 ║ 0 ║ 3 ║ 0 ║ 72 ║ 0 ║ 10 ║ 3 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:25:17 ║ 5 ║ 0 ║ 5 ║ 0 ║ 77 ║ 100 ║ 13 ║ 5 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:25:32 ║ 0 ║ 0 ║ 0 ║ 0 ║ 100 ║ 0 ║ 0 ║ 0 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:25:36 ║ 0 ║ 0 ║ 0 ║ 0 ║ 92 ║ 0 ║ 8 ║ 0 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:27:24 ║ 48 ║ 48 ║ 0 ║ 0 ║ 0 ║ 0 ║ 5 ║ 0 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:27:54 ║ 0 ║ 0 ║ 0 ║ 0 ║ 0 ║ 100 ║ 0 ║ 0 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:28:11 ║ 62 ║ 8 ║ 3 ║ 0 ║ 15 ║ 0 ║ 13 ║ 3 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:28:53 ║ 35 ║ 0 ║ 6 ║ 0 ║ 37 ║ 0 ║ 23 ║ 6 ║ ║ 64e8394876a5b7f1 ║ October, 28 2015 08:29:16 ║ 54 ║ 2 ║ 0 ║ 0 ║ 10 ║ 0 ║ 35 ║ 0 ║ ║ e86b0b91546194cc ║ October, 28 2015 08:24:41 ║ 13 ║ 13 ║ 69 ║ 3 ║ 0 ║ 100 ║ 5 ║ 67 ║ ║ e86b0b91546194cc ║ October, 28 2015 08:33:33 ║ 0 ║ 0 ║ 100 ║ 0 ║ 0 ║ 0 ║ 0 ║ 100 ║ ║ e86b0b91546194cc ║ October, 28 2015 08:33:38 ║ 0 ║ 0 ║ 100 ║ 0 ║ 0 ║ 0 ║ 0 ║ 100 ║ ║ e86b0b91546194cc ║ October, 28 2015 08:34:06 ║ 19 ║ 6 ║ 31 ║ 2 ║ 29 ║ 0 ║ 16 ║ 29 ║ ║ e86b0b91546194cc ║ October, 28 2015 08:34:34 ║ 3 ║ 0 ║ 0 ║ 0 ║ 95 ║ 0 ║ 3 ║ 0 ║ ╚═══════════════════╩════════════════════════════╩═════════════╩═════════════╩══════════╩══════════╩════════╩══════════╩══════════╩═════════╝

COALESCE也是多余的（如果只允许正/零值）：

SELECT end_user_id, tms, MAX(CASE WHEN type = 'IN_VEHICLE' THEN confidence ELSE 0 END) AS IN_VEHICLE, MAX(CASE WHEN type = 'ON_BICYCLE' THEN confidence ELSE 0 END) AS ON_BICYCLE, MAX(CASE WHEN type = 'ON_FOOT' THEN confidence ELSE 0 END) AS ON_FOOT, MAX(CASE WHEN type = 'RUNNING' THEN confidence ELSE 0 END) AS RUNNING, MAX(CASE WHEN type = 'STILL' THEN confidence ELSE 0 END) AS STILL, MAX(CASE WHEN type = 'TILTING' THEN confidence ELSE 0 END) AS TILTING, MAX(CASE WHEN type = 'UNKNOWN' THEN confidence ELSE 0 END) AS UNKNOWN, MAX(CASE WHEN type = 'WALKING' THEN confidence ELSE 0 END) AS WALKING FROM activities GROUP BY end_user_id, tms ORDER BY end_user_id, tms;

的 SqlFiddleDemo2

您还可以考虑为type列创建查找表，而不是直接存储在表格字符串activities_type (type_id, type_name)中。

附录

我不是Postgresql Expert但经过一些游戏之后：

('IN_VEHICLE', 'ON_BICYCLE', ...)

为什么要连接并拆分SELECT LEFT(end_user_id, strpos(end_user_id, '_')-1) AS end_user_id, RIGHT(end_user_id, LENGTH(end_user_id) - strpos(end_user_id, '_'))::timestamp AS tms, COALESCE(IN_VEHICLE,0) AS IN_VEHICLE, COALESCE(ON_BICYCLE,0) AS ON_BICYCLE, COALESCE(ON_FOOT,0) AS ON_FOOT, COALESCE(RUNNING,0) AS RUNNING, COALESCE(STILL,0) AS STILL, COALESCE(TILTING,0) AS TILTING, COALESCE("UNKNOWN",0) AS "UNKNOWN", COALESCE(WALKING,0) AS WALKING FROM crosstab( 'SELECT (end_user_id || ''_'' || tms) AS row_id, type, confidence FROM activities ORDER BY row_id, type, confidence', 'SELECT DISTINCT type FROM activities order by type' ) AS newtable ( end_user_id text, IN_VEHICLE int, ON_BICYCLE int, ON_FOOT int, RUNNING int, STILL int, TILTING int, "UNKNOWN" int, WALKING int) ORDER BY end_user_id, tms;？

因为end_user_id + tms需要：

crosstab(text,text)

请注意，此版本中没有row_id <=> end_user_id + tms category <=> type value <=> confidence。

附录2 - 最终版本

基于tablefunc module doc GROUP BY：

这样做要好得多，因为它可以处理F.37.1.4. crosstab(text, text)。所以现在：

row_id, extra_col1, extra_col2, category, value)

最终查询：

row_id <=> id extra_col1 <=> end_user_id extra_col2 <=> tms ...

activities_type表有什么意义？

数据库规范化，您可以使用：

SELECT end_user_id, tms, coalesce(max(IN_VEHICLE), 0) as IN_VEHICLE, coalesce(max(ON_BICYCLE), 0) as ON_BICYCLE, coalesce(max(ON_FOOT), 0) as ON_FOOT, coalesce(max(RUNNING), 0) as RUNNING, coalesce(max(STILL), 0) as STILL, coalesce(max(TILTING), 0) as TILTING, coalesce(max("UNKNOWN"), 0) as "UNKNOWN", coalesce(max(WALKING), 0) as WALKING FROM crosstab( 'SELECT id,end_user_id , tms, type, confidence FROM activities', 'SELECT DISTINCT type FROM activities order by type' ) AS newtable ( id INT, end_user_id text, tms timestamp, IN_VEHICLE int, ON_BICYCLE int, ON_FOOT int, RUNNING int, STILL int, TILTING int, "UNKNOWN" int, WALKING int ) GROUP BY end_user_id, tms ORDER BY end_user_id, tms;

此版本使用SELECT DISTINCT type FROM activities order by type vs SELECT type_name FROM activities_types ORDER BY type_name;作为id，因此仍然需要row_id来压缩多行。

总结：条件聚合是最具可读性的解决方案。

Postgresql 9.3：如何使用带有多个索引的交叉表？

1 个答案:

附录

附录2 - 最终版本