[英]Fetch Column Names of a Table for Columns with Top 3 count
我需要一个表中的列名称,这些列是具有最高计数的前三列。
我正在使用mySQL:
我能够使用此查询获取所需列的计数:
SELECT
COUNT(unsafe_spaces_home) AS AH ,
COUNT(unsafe_spaces_school) AS SCH ,
COUNT(unsafe_spaces_market_place) AS MP ,
COUNT(unsafe_spaces_field_or_playground) AS PG ,
COUNT(unsafe_spaces_dumping_ground) AS DG ,
COUNT(unsafe_spaces_railway_station) AS RS ,
COUNT(unsafe_spaces_route_to_toilet) AS RT ,
COUNT(unsafe_spaces_toilet) AS ST ,
COUNT(unsafe_spaces_well_or_water_pump) AS WT ,
COUNT(unsafe_spaces_river_pond) AS RP ,
COUNT(unsafe_spaces_sewer) AS SS
FROM formdata
我得到的结果如下:
AH SCH MP PG DG RS RT ST WT RP SS
===========================================
0 0 12 1 7 16 2 9 0 9 1
但是我需要这样的结果:
top_3_columns
================
RS,MP,ST
我怎样才能做到这一点?
将列名称视为a,b,c,d和e然后您可以使用以下查询
select tagName, value from
(select 'a' tagName, count(a) value from formdata UNION
select 'b' tagName, count(b) value from formdata UNION
select 'c' tagName, count(c) value from formdata UNION
select 'd' tagName, count(d) value from formdata UNION
select 'e' tagName, count(e) value from formdata
)
as results
order by value desc
limit 3;
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