如何解决sql-按范围分组以包括没有值的范围
尝试以下查询(也在SQL Fiddle上):
WITH ranges AS (
SELECT (ten*10)::text||'-'||(ten*10+9)::text AS range,
ten*10 AS r_min, ten*10+9 AS r_max
FROM generate_series(0,9) AS t(ten))
SELECT r.range, count(s.*)
FROM ranges r
LEFT JOIN scores s ON s.score BETWEEN r.r_min AND r.r_max
GROUP BY r.range
ORDER BY r.range;
您可以通过将参数更改为轻松调整范围generate_series()
。可以使用以下构造来确保ranges
始终覆盖您的分数:
SELECT (ten*10)::text||'-'||(ten*10+9)::text AS range,
ten*10 AS r_min, ten*10+9 AS r_max
FROM generate_series(0,(SELECT max(score)/10 FROM scores)) AS t(ten))
对于ranges
CTE。
解决方法
假设有一个与此问题类似的情况。我想得到以下结果:
score range | number of occurrences
-------------------------------------
0-9 | 11
10-19 | 14
20-29 | 3
... | ...
我可以使用选定的答案作为解决方案:
select t.range as [score range],count(*) as [number of occurences]
from (
select case
when score between 0 and 9 then ' 0- 9'
when score between 10 and 19 then '10-19'
else '20-99' end as range
from scores) t
group by t.range
我如何确保即使在该范围内没有任何结果,也将显示30-39的分数范围?
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