Working with Combined Knowledge Sorts inside a Discipline Utilizing Rockset

So… you assume all of your knowledge in a selected subject are a string kind, however while you attempt to run your question, you get some errors. Doing extra investigation, it seems like you may have some int and undefined varieties as properly. Bummer…

Despair not! We will really work round this (with out knowledge prep 😉). To recap, in our first weblog, we created an integration with MongoDB on Rockset, so Rockset can learn and [update] the info coming in MongoDB. As soon as the info is in Rockset, we will run SQL on schemaless and unstructured knowledge.

The information:

Embedded content material: https://gist.github.com/nfarah86/ef1cc9da88e56226c4c46fd0e3c8e16e

We have an interest within the release_date subject: "release_date": "1991-06-07".

The question:

Rockset has a operate referred to as DATE_PARSE(), which lets you flip a string formatted date right into a date object. If you wish to order films by simply the yr, you should utilize EXTRACT().

Basically, when you flip your string formatted date right into a date object, you possibly can then extract the yr.

At first look, this appears fairly simple to unravel— in the event you wished to order all of the film titles by the discharge yr, you possibly can write one thing like this:

SELECT
      t.title, t.release_date
FROM
    commons.TwtichMovies t
ORDER BY
    EXTRACT(
         YEAR
         FROM
         DATE_PARSE(t.release_date, '%Y-%m-%d')
    ) DESC
;

When working this question, we get a timestamp parsing error:
Error [Query]
Timestamp parse error:

This might imply you’re working with different knowledge varieties that aren’t strings. To examine, you possibly can write one thing like this:

SELECT
      t.title, TYPEOF(t.release_date)
FROM
    commons.TwtichMovies t
WHERE 
    TYPEOF(t.release_date) != 'string'
;

That is what we get again:

Now, that we all know what’s inflicting the error, we will re-write the question to discard something that’s not a string kind— proper 🤗?

SELECT
      t.title, t.release_date
FROM
    commons.TwtichMovies t
WHERE
    TYPEOF(t.release_date) = 'string';
ORDER BY
     EXTRACT(
          YEAR
          FROM
              DATE_PARSE(t.release_date, '%Y-%m-%d')
     )DESC
;

WRONG 🥺! This really returns a timestamp parsing error as properly:

Error [Query]
Timestamp parse error

You are most likely saying to your self, “what the heck.” One case we didn’t consider earlier is that there could possibly be empty strings 🤯- If we run the next question:

SELECT DATE_PARSE('', '%Y-%m-%d');

We get the identical timestamp parsing error again:

Error [Query]
Timestamp parse error

Aha.

How can we really write this question to keep away from the timestamp parsing errors? Right here, we will really verify the LENGTH() of the string and filter out all the things that doesn’t meet the size requirement— so one thing like this:

WHERE LENGTH(t.release_date) = 10

We will additionally TRY_CAST() t.release_date to a string. If the sector worth can’t be was a string, a null worth is returned (i.e. it gained’t error out). Placing this all collectively, we will technically write one thing like this:

SELECT
    t.title,
    t.release_date
FROM
    commons.TwtichMovies t
WHERE
    TRY_CAST(t.release_date AS string) will not be null
    AND LENGTH(TRY_CAST(t.release_date AS string)) = 10
ORDER BY
    EXTRACT(
         YEAR
         FROM
         DATE_PARSE(t.release_date, '%Y-%m-%d')
    )
;

Voila! it really works!

Through the stream, I really wrote a extra difficult model of this question. The above question and the question within the stream are equal. We additionally wrote queries that combination! You’ll be able to catch the total breakdown of the session under:

Embedded content material: https://youtu.be/PGpEsg7Qw7A

TLDR: yow will discover all of the sources you must get began on Rockset within the developer nook.