寻找在蜂巢中设置一个可重用的变量

问题描述

我正在寻找一个如下所示的变量，称为today_date，然后能够在整个查询中将其作为变量重用.以下引发错误.

I'm looking to set a variable like below, called today_date, and then be able to reuse it as a variable throughout the query. The below throws an error.

set today_date = date_format(date_sub(current_date, 1), 'YYYYMMdd')

select account
from table
where data_date = today_date

推荐答案

您仍然需要在set行的末尾添加分号，并用${}包围变量并使用正确的命名空间.

You still need to put a semicolon at the end of the set line, surround your variable with ${} and use the proper namespace.

请注意，定义变量后，这将不执行date_format()函数.当您使用变量时，SQL代码将照原样复制.可以将它更多地看作是宏而不是变量.

Note that this will not execute the date_format() function when the variable is defined. When you use the variable the SQL code will just be copied as-is. Think of it as more as a macro than as a variable.

此外，Hive具有多个变量名称空间.最简单的2个选项是，在定义变量时不那么冗长，而在使用变量时(hiveconf名称空间)则更冗长:

Furthermore, Hive has multiple variable namespaces.The 2 easiest options are either to be less verbose when you define your variable but to be more verbose when you use it (hiveconf namespace):

set today_date = date_format(date_sub(current_date, 1), 'YYYYMMdd');
select account from table where data_date = ${hiveconf:today_date};

或相反(hivevar名称空间)

or the other way round (hivevar namespace)

set hivevar:today_date = date_format(date_sub(current_date, 1), 'YYYYMMdd');
select account from table where data_date = ${today_date};

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