前言前几篇我们讲解了ODPS数据开发过程中会大量用到的各种日期与字符、数学运算、聚合、开窗、自定义等函数，今天我们针对海量数据开发过程数据开发效率优化做讲解。常见数据优化问题数据倾斜问题 1、大表关联小表大表关联小表出现倾斜时，可以使用mapjoin的hint(/+mapjoin(b)/)。同时可适当调整mapjoin中小表的内存大小： set odps.sql.mapjoin.mem...

文章 2022-12-17 来自：开发者社区

阿里云-DataWorks- ODPS SQL开发2

前言我们在DataWorks空间下做数据开发时会经常用到大量的函数，本文主要讲解日常大量会接触到的一些。常用函数与关键词：1、coalesce（expr1，expr2）返回列表中第一个非null的值2、concat（string A，string B）将参数中的所有字符串连接在一起如果没有参数或者有某个参数为null就返回null3、cast（expr as ）将表达式的结果...

文章 2022-12-17 来自：开发者社区

ODPS SQL用户最熟悉使用SQL对数据分析了。ODPS也支持SQL查询操作，而且语法类似于Hive 的HQL。SQL操作的主要对象是表，数据量可在T级到P级。SQL中提供的功能有：DLL：表、列、分区、视图、生命周期等操作；DML：数据更新、多路输出以及动态分区输出；Join：多表关联分析，支持 inner , left , right full join 以及mapjoin;窗口函数：....

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