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Projections are a query-optimization feature of MergeTree tables in ClickHouse that store data in a different format than the defined sort order. Useful use cases include the ability to sort the data in a different order than the primary key, and also to pre-aggregate columns. One nice benefit of projections over materialized views is that a projection does not require a separate table, so users simply query the original table and ClickHouse decides at query time if a projection can improve the performance.

Rich Raposa
Director, Global Learning, ClickHouse

How to Optimize a ClickHouse Query using Projections

Linux, macOS, FreeBSD

Query parameters allow you to write generic queries that contain abstract placeholders instead of concrete identifiers. In this video, we discuss the details of how to define and use query parameters in ClickHouse.

How to Use Query Parameters in ClickHouse

Do you have Parquet files that you want to insert into a ClickHouse table? That's easy to do with ClickHouse, no matter where your Parquet files are stored.

Videos / How to

How to Query and Ingest Parquet Files with ClickHouse

Rich Raposa Director, Global Learning, ClickHouse

Recent videos