March 2021
Intermediate to advanced
265 pages
6h 50m
Chinese
Content preview from Presto实战
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.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.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.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.
116
｜
第
8
章
此外，创建的连接通常使用特定的用户或其他授权机制，即存在特定的限制。如果用
户没有除读取数据以外的权限，或者甚至只能从特定的
schema
中读取数据，那么其他
操作（如删除数据或写入新数据）就会执行失败。
8.1
Presto
语句
在使用
Presto
深入查询数据之前，知道哪些数据可用、在什么地方、是什么类型很重要。
你可以通过
Presto
语句
（
Presto
statement
）收集这些信息。
Presto
语句可以查询系统表和源
数据，以获取
catalog
和
schema
等信息。这些语句与所有
SQL
语句在相同的上下文工作。
语句中的
FROM
和
FOR
子句需要输入一个完全限定的表、
catalog
或
schema
，除非之前使用
USE
设置了默认值。
LIKE
子句可以用来限制结果，其使用的
schema
匹配语法类似于
SQL
中的
LIKE
命令。
[]
中的命令部分是可选的。以下是
Presto
可用的一些语句。
SHOW CATALOGS [ LIKE
pattern
]
列出可用的
catalog
。
SHOW SCHEMAS [ FROM
catalog
] [ LIKE
pattern
]
列出
catalog
中的
schema
。
SHOW TABLES [ FROM
schema
] [ LIKE
pattern
]
列出一个
schema
中的表。
SHOW FUNCTIONS
显示所有可用
SQL
函数的列表。
SHOW COLUMNS FROM
table
或
DESCRIBE
table
列出表中的列及其数据类型和其他属性。 ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.