March 2021
Intermediate to advanced
265 pages
6h 50m
Chinese
Content preview from Presto实战
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在
Presto
中使用
SQL
｜
141
Presto
可以使用隐式
CrossJoin
：用一个以逗号分隔表名的列表定义
Join
在一起的表，并用
WHERE
子句来定义
Join
条件。
SELECT custkey, mktsegment, nation.name AS nation
FROM tpch.tiny.nation, tpch.tiny.customer
WHERE nation.nationkey = customer.nationkey;
custkey | mktsegment | name
---------+------------+-----------
108 | BUILDING | ETHIOPIA
106 | MACHINERY | ARGENTINA
101 | MACHINERY | BRAZIL
Join
是查询处理中开销最大的操作之一。当一个查询中存在多个
Join
时，可以以不同的顺
序处理这些
Join
。
TPCH
基准中的
Q09
查询就是一个很好的复杂查询示例：
SELECT
nation,
o_year,
sum(amount) AS sum_profit
FROM (
SELECT
N.name AS nation,
extract(YEAR FROM o.orderdate)AS o_year,
l.extendedprice * (1 - l.discount) - ps.supplycost * l.quantity AS amount ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.