17

我有一个看起来像这样的视图

          value1count     value2count value3count
          ----------------------------------------
             25              35          55

我需要将列标题转换成行，所以我需要它看起来像

          Values              Count
         -----------------------------
           value1count         25
           value2count         35
           value3count         55

我可以通过选择单个列名作为第一列和数据作为第二列来做到这一点，然后对所有列进行相同的联合。

有一个更好的方法吗？我正在使用 PosgreSQL 8.1，因此没有可以使用的枢轴运算符。

感谢您提前回复。

4

5 回答 5

41

Crosstab only does the reverse of what you need, but this should help you:

First create the unnest() function that is included in 8.4, see here for instructions.

Then you can do this (based on this post):

SELECT
   unnest(array['value1Count', 'value2Count', 'value3Count']) AS "Values",
   unnest(array[value1Count, value2Count, value3Count]) AS "Count"
FROM view_name
ORDER BY "Values"

I can verify that this works in 8.4, but because I don't have 8.1, I can't promise it will work the same.

于 2012-05-16T19:24:10.283 回答
8

我通过使用hstore的功能实现了您的目标：

SELECT (x).key, (x).value
FROM
  ( SELECT EACH(hstore(t)) as x
    FROM   t
  ) q;

如果您的“待展开”视图或表（此处称为t）中有多行，您可能需要在中间表中插入一个附加标识符q，例如：

SELECT id, (x).key, (x).value
FROM
  ( SELECT id, EACH(hstore(t)) as x
    FROM   t
  ) q;

参考：hstore文档

于 2014-01-15T09:01:11.813 回答
5

我正在寻找与此类似的操作，以更轻松地处理来自 bash 脚本的表信息。事实证明，告诉 psql 将表列显示为行非常容易：

psql mydbname -x -A -F= -c "select * from blah where id=123"
  • 这-x就是输出的枢轴。
  • -A删除额外的间距。
  • 列名和值之间的替换-F=为|。=

这当然不会在 SQL 中工作，它只会修改psql格式化输出的方式。

于 2016-03-16T18:52:35.120 回答
1

我也有类似的情况。UNION ALL我将查询包装在 with 语句中，然后为每一行做一堆s 。在我的情况下，如果我有多个记录，则 ncm_id 会有所不同，因此我继续将其添加到结果集中的列列表中。这可能不是最好的方法，但它适用于我的用例。

 WITH query_a AS (
     SELECT
       fin_item.item_number || ' - ' || fin_item.item_descrip1 fin_item,
       fin_ls.ls_number,
       ls_sort.sortby_employeeid,
       ls_sort.ncm_id,
       ls_sort.created_at,
       ls_sort.updated_at,
       ls_sort.sort_qty,
       ls_sort.initial_scan_time,
       ls_sort.ncm_scan_time,
       ls_sort.badge_scan_time,
       ls_sort.computer_name,
       ls_sort.number_of_ops,
       ls_sort.ncm_item_scan_time,
       sort_by.name sort_by,
       tblncm.instructions,
       tblncm.ncm_comments
     FROM public.item AS fin_item
       INNER JOIN public.ls AS fin_ls ON fin_item.item_id = fin_ls.ls_item_id
       INNER JOIN stone.ls_sort ON fin_ls.ls_id = ls_sort.ls_id
       INNER JOIN stone.vw_mssql_employees AS sort_by ON ls_sort.sortby_employeeid = sort_by.employeeid
       INNER JOIN stone.tblncm ON ls_sort.ncm_id = tblncm.ncm_id
       LEFT JOIN stone.equips AS mach_equips ON ls_sort.mach_equip_id = mach_equips.id
       LEFT JOIN stone.equips AS mold_equips ON ls_sort.mold_equip_id = mold_equips.id
     WHERE 1 = 1
           AND fin_ls.ls_number ILIKE 'S143027526190' || '%'
 )
   SELECT *
   FROM (
     (SELECT 'fin_item' my_column, fin_item::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'ls_number' my_column, ls_number::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'sortby_employeeid' my_column, sortby_employeeid::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'ncm_id' my_column, ncm_id::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'created_at' my_column, created_at::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'updated_at' my_column, updated_at::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'sort_qty' my_column, sort_qty::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'initial_scan_time' my_column, initial_scan_time::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'ncm_scan_time' my_column, ncm_scan_time::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'badge_scan_time' my_column, badge_scan_time::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'computer_name' my_column, computer_name::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'number_of_ops' my_column, number_of_ops::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'ncm_item_scan_time' my_column, ncm_item_scan_time::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'sort_by' my_column, sort_by::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'instructions' my_column, instructions::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
      UNION ALL
     (SELECT 'ncm_comments' my_column, ncm_comments::TEXT my_value, ncm_id::TEXT my_ncm FROM query_a)
   ) as query_guy
 ORDER BY my_ncm;
于 2017-11-21T18:39:32.530 回答
0

我可能不明白......但我这样做的方式是也选择 DISTINCT 然后选择我需要的平均列值。像这样：

SELECT DISTINCT contributing_factor_vehicle_1, AVG(number_of_cyclist_injured) FROM "table1".motor_vehicle_collisions_crashes 
GROUP BY contributing_factor_vehicle_1
ORDER BY avg(number_of_cyclist_injured) desc

这就是创造了这样的东西： 在此处输入图像描述

顺便说一句，这是纽约市机动车碰撞数据。

于 2020-02-26T19:25:51.553 回答