March 2021
Intermediate to advanced
265 pages
6h 50m
Chinese
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高级
SQL
特性
｜
169
SELECT species, sepal_length_cm,
avg(sepal_length_cm) OVER(PARTITION BY species) AS avgsepal
FROM memory.default.iris;
species | sepal_length_cm | avgsepal
------------+---------------+----------
setosa | 5.1 | 5.006
setosa | 4.9 | 5.006
setosa | 4.7 | 5.006
...
virginica | 6.3 | 6.588
virginica | 5.8 | 6.588
virginica | 7.1 | 6.588
...
平均长度因品种而异。借助
DISTINCT
，通过省略单个长度，你可以得到每个品种的平均长
度列表：
SELECT DISTINCT species,
avg(sepal_length_cm) OVER(PARTITION BY species) AS avgsepal
FROM memory.default.iris;
species | avgsepal
------------+----------
setosa | 5.006
virginica | 6.588
versicolor | 5.936
(3 rows)
Presto
中的窗函数支持所有的聚合函数以及许多窗特有的函数： ...