问题：

如果事先确定列数 ，如何计算多列中每行的汇总函数（例如avg()或sum()）？

我已将输入表panel_stats_rnd csv和DLL创建为here。

我想计算每一行rnd_avg_parcelcount作为所有列c_1_avg_parcelcount，c_2_avg_parcelcount，...的平均值，其中我可以有任意数字的输入表（比如说100） _avg_parcelcount的列。对于列rnd_sum_parcelcount，我想计算以sum()开头并以c_结尾的所有列的_sum_parcelcount。

表格如下：

SELECT * FROM panel_stats_rnd; gid | d | dist_from | dist_to | distlabel | rnd_avg_parcelcount | rnd_sum_parcelcount | rnd_avg_callcount | rnd_sum_callcount | rnd_avg_perccalled | called_avg_parcelcount | called_sum_parcelcount | called_avg_callcount | called_sum_callcount | called_avg_perccalled | c_1_avg_parcelcount | c_1_sum_parcelcount | c_1_avg_callcount | c_1_sum_callcount | c_1_avg_perccalled | c_2_avg_parcelcount | c_2_sum_parcelcount | c_2_avg_callcount | c_2_sum_callcount | c_2_avg_perccalled -----+----+-----------+---------+-----------+---------------------+---------------------+-------------------+-------------------+--------------------+------------------------+------------------------+----------------------+----------------------+-----------------------+---------------------+---------------------+-------------------+-------------------+----------------------+---------------------+---------------------+-------------------+-------------------+---------------------- 1 | 0 | 0 | 100 | 0-100 | | | | | | 119045 | 119045 | 119045 | 23 | 0.000193204250493511 | 119045 | 119045 | 119045 | 16 | 0.000134402956865051 | 119045 | 119045 | 119045 | 16 | 0.000134402956865051 2 | 1 | 100 | 200 | 100-200 | | | | | | 163140 | 163140 | 163140 | 22 | 0.000134853500061297 | 163140 | 163140 | 163140 | 17 | 0.000104204977320093 | 163140 | 163140 | 163140 | 18 | 0.000110334681868334 3 | 2 | 200 | 300 | 200-300 | | | | | | 135934 | 135934 | 135934 | 10 | 7.3565112481057e-05 | 135934 | 135934 | 135934 | 18 | 0.000132417202465903 | 135934 | 135934 | 135934 | 15 | 0.000110347668721585 4 | 3 | 300 | 400 | 300-400 | | | | | | 116874 | 116874 | 116874 | 13 | 0.000111230898232284 | 116874 | 116874 | 116874 | 11 | 9.41184523503944e-05 | 116874 | 116874 | 116874 | 18 | 0.000154012012937009 5 | 4 | 400 | 500 | 400-500 | | | | | | 93216 | 93216 | 93216 | 12 | 0.000128733264675592 | 93216 | 93216 | 93216 | 10 | 0.000107277720562993 | 93216 | 93216 | 93216 | 12 | 0.000128733264675592 6 | 5 | 500 | 600 | 500-600 | | | | | | 69992 | 69992 | 69992 | 7 | 0.0001000114298777 | 69992 | 69992 | 69992 | 10 | 0.000142873471253858 | 69992 | 69992 | 69992 | 7 | 0.0001000114298777 7 | 6 | 600 | 700 | 600-700 | | | | | | 50816 | 50816 | 50816 | 10 | 0.000196788413098237 | 50816 | 50816 | 50816 | 6 | 0.000118073047858942 | 50816 | 50816 | 50816 | 0 | 0 8 | 7 | 700 | 800 | 700-800 | | | | | | 34814 | 34814 | 34814 | 0 | 0 | 34814 | 34814 | 34814 | 6 | 0.000172344459125639 | 34814 | 34814 | 34814 | 4 | 0.000114896306083759 9 | 8 | 800 | 900 | 800-900 | | | | | | 23023 | 23023 | 23023 | 1 | 4.34348260435217e-05 | 23023 | 23023 | 23023 | 4 | 0.000173739304174087 | 23023 | 23023 | 23023 | 1 | 4.34348260435217e-05 10 | 9 | 900 | 1000 | 900-1000 | | | | | | 14215 | 14215 | 14215 | 1 | 7.03482237073514e-05 | 14215 | 14215 | 14215 | 1 | 7.03482237073514e-05 | 14215 | 14215 | 14215 | 5 | 0.000351741118536757 11 | 10 | 1000 | 5000 | 1000-5000 | | | | | | 23527 | 23527 | 23527 | 0 | 0 | 23527 | 23527 | 23527 | 0 | 0 | 23527 | 23527 | 23527 | 3 | 0.000127513070089684 (11 rows)

我尝试了以下2列（有效，但我不想为100列写5次，除了列数必须是参数）：

SELECT d,c_1_avg_parcelcount,c_2_avg_parcelcount, (SELECT avg(c) FROM (VALUES (c_1_avg_parcelcount) , (c_2_avg_parcelcount) ) T (c)) AS Avg_, (SELECT sum(c) FROM (VALUES (c_1_avg_parcelcount) , (c_2_avg_parcelcount) ) T (c)) AS sum_ FROM panel_stats_rnd;

我也尝试过以下但不起作用。

WITH cols AS ( select value(column_name) from information_schema.columns where table_name = 'panel_stats_rnd' AND column_name SIMILAR TO 'c_%avg_parcelcount' AND column_name != 'called_avg_parcelcount' ) SELECT *, (SELECT avg(Col) FROM cols V(Col) ) AS col_average FROM panel_stats_rnd;

我快到了，但有些东西不见了......

Answer 1

select
  *,
  (select avg(v::numeric)
     from json_each_text(row_to_json(panel_stats_rnd.*)) as j(k,v)
    where k like 'c\_%\_avg\_parcelcount') as rnd_avg_parcelcount,
  (select sum(v::numeric)
     from json_each_text(row_to_json(panel_stats_rnd.*)) as j(k,v)
    where k like 'c\_%\_sum\_parcelcount') as rnd_sum_parcelcount
from
  panel_stats_rnd;

查看有关所涉及功能的documentation。

基础字符（\_）有转义符，因为对于like运算符，它意味着任何单个字符，例如select 'a' like '_';为{{1} }。

PostgreSQL聚合函数，用于跨越多个未知数量的列的每一行

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