如何生成包含今天日期的表名？

Question

It may seem a little strange, but there are already tables with names for each date.

In my project, I have tables for each date to make statistics easier to handle.

Of course, I don't think this is always the best way, but this is the table structure for my project. (It's a common technique in Google BigQuery and Amazon Athena. This question is about Google BigQuery)

So to get the data, I want to generate today's date. If I use TODAY , I can get the data of the latest day without rewriting the code even if it is the next day.

I tried, but the code didn't work.

Not work 1:

CONCAT in FROM

SELECT
  *
FROM
  CONCAT('foo_', FORMAT_TIMESTAMP('%Y%m%d', CURRENT_TIMESTAMP(), 'Asia/Tokyo'))

Error:

Table-valued function not found: CONCAT at [4:3]

Not work 2:

create temporary function :

create temporary function getTableName() as (CONCAT('foo_', FORMAT_TIMESTAMP('%Y%m%d', CURRENT_TIMESTAMP(), 'Asia/Tokyo')));

Error:

CREATE TEMPORARY FUNCTION statements must be followed by an actual query.

Question

How do I generate a table name that contains TODAY 's date?

Answer 1

In this case, I would recommend you to useWild tables in BigQuery , which allows you to use some features in Standard SQL.

With Wild Tables you can use _TABLE_SUFFIX , it grants you the ability to filter/scan tables containing this parameter. The syntax would be as follows:

SELECT *
FROM `test-proj-261014.sample.test_*` 
where _TABLE_SUFFIX = FORMAT_DATE('%Y%m%d', CURRENT_DATE)

I hope it helps.

Answer 2

Your first query should go like this:

select CONCAT('foo_', FORMAT_TIMESTAMP('%Y%m%d', CURRENT_TIMESTAMP(), 'Asia/Tokyo'))

For creating temporary function, use the below code:

create temp function getTableName() as
((select CONCAT('foo_', FORMAT_TIMESTAMP('%Y%m%d', CURRENT_TIMESTAMP(), 'Asia/Tokyo'))
));
select getTableName()

The error "CREATE TEMPORARY FUNCTION statements must be followed by an actual query." is because once the temporary functions are defined then you have to use the actual query to use that function and then the validity of function dies out. To define persistent UDFs and use them in multiple queries please go through the link to define permanent functions.You can reuse persistent UDFs across multiple queries, whereas you can only use temporary UDFs in a single query.