Hydrolix SQL Statements

In Hydrolix, data is organized by project and table. In the bucket used when the system was setup, there is a path structure that looks

bucket_name/db/hdx

Under hdx are project folders. In any initial deployment, the project default should exist. Under default there should be one table called default_table. If you are ever unsure about the names of projects or tables, you can browse the bucket structure to find the names.

Table Statements

Two table commands are available in Hydrolix,

  • exists tablename
  • describe tablename

Required Statement Clauses

SELECT is currently the only type of statement supported by Hydrolix

The mandatory parts of statements in Hydrolix SQL are:

SELECT
FROM
WHERE

Each are described below.

SELECT

SELECT statements work as expected. They allow you to choose which data you want from a data set. It can include column names and function calls.

FROM

FROM specifies where the data should come from. In Hydrolix, that requires a :

  • Project Name
  • Table Name
  • View Schema Name (Optional)

The FROM clause ends up looking like:

SELECT
FROM project_name.table_name#my_view
WHERE

If a default view schema is defined on a table, it does not have to be specified as part of the query:

SELECT
FROM project_name.table_name
WHERE

WHERE

WHERE clauses in Hydrolix are required, and must contain the primary index defined in the ingest transform schema. It can contain other conditions as well, but MUST contain a test on the primary index.

SELECT count(timestamp) AS count
  FROM my_first_project.the_table#the_view
  WHERE (timestamp BETWEEN1977-04-25 00:00:00AND2010-04-25 23:00:00)

Optional Statement Clauses

WITH

With statements allow you to create a named sub-query for use later in the select statement. They come before the SELECT statement so the result can be used in the rest of the query.

WITH [subquery] AS unique_name
...

HAVING

HAVING is a statement where conditions areapplied after an aggregation is complete. TheWHERE statement conditions are applied before an aggregation. HAVING statements are applie after.

GROUP BY

The GROUP BY statement groups data together inrows. For example, you could query all incidents for a time period, grouping on incident type to get totals for each type of incident in a given time period.

ORDER BY

ORDER BY is used to sort the result set. Takes values:

  • asc
  • desc

If neither is specified, asc is assumed.

IN

Used to test if a value is in a set.

SELECT avg(score) 

FROM my_project.my_table WHERE "the_user_name" IN
['user1', 'user2', 'user3'] AND timestamp
BETWEEN....

would calculate the average of the score column for those 3 users.

LIMIT

LIMIT the number of rows returned. It must be the last statement in SQL statement.

SELECT
FROM
WHERE
...
LIMIT 10