In this lesson we will:
- Lesson contents 1
- Lesson contents 2
- Lesson contents 3
ClickHouse allows us query data that is stored outside of ClickHouse in formats such as Parquet, Iceberg, Delta, CSV etc.
This is useful in a few situatoins.
Firstly, if we want to ingest that data into ClickHouse, it is sometimes useful to query it and then use that query as the basis for the ingest.
select * from
We may also wish to. One example of this is when we maintain a data lake.
The usual mechanism for querying data held within a database or data warehouse is to ingest the data into the database and let it manage it for us.
Icnreasingly however, many companies are looking to decouple this, and store their data in other formats such as Parquet.
In some intsances, they are running a data lake, and want to keep this data avaialble.
In this instance, it is useful to treat our database as a query engine, and allow us to query data that is stored elsewhere.
Querying is easy
select * from file ()