July 2023
Intermediate to advanced
278 pages
5h 40m
Chinese
Content preview from Trino 权威指南：原书第2版
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在
Trino
中使用
SQL
|
155
WHERE
子句的条件由一个或多个布尔表达式组成，这些表达式由
AND
和
OR
相连。
SELECT custkey, acctbal
FROM tpch.sf1.customer WHERE acctbal < 0;
custkey | acctbal
---------+---------
75016 | -735.89
75027 | -399.78
75028 | -222.92
75034 | -679.38
75037 | -660.07
...
SELECT custkey, acctbal FROM tpch.sf1.customer
WHERE acctbal > 0 AND acctbal < 500;
custkey | acctbal
---------+---------
75011 | 165.71
75012 | 41.65
75021 | 176.2
75022 | 348.24
75026 | 78.64
...
WHERE
子句的条件很重要，因为它可用于多种查询优化。在
4.8
节中，你可以了解更多
关于查询优化的内容。当查询多个表时，你可以通过
WHERE
子句中的条件将它们连接起
来。
Trino
使用这些信息来决定高效的查询执行计划。
8.12 GROUP BY
和
HAVING
子句
GROUP BY
和
HAVING
子句在分析型查询中非常常用。
GROUP BY
用于将具有相同值的行合
并成一行：
SELECT mktsegment
FROM tpch.sf1.customer ...
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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.