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Data & Analytics · Intermediate

Delta Lake

An open-source table format that adds ACID transactions, schema enforcement and evolution, time travel and MERGE to Parquet files.

Definition

Delta Lake stores data as Parquet plus a _delta_log of JSON commits and checkpoints. It is the default table format in Databricks and Microsoft Fabric (OneLake). It supports streaming and batch on the same table, OPTIMIZE, VACUUM, Z-ordering, liquid clustering and Change Data Feed.

Example

CREATE TABLE sales USING DELTA AS SELECT * FROM raw_sales;

Exam tip

In Fabric and Databricks, tables are Delta by default; the _delta_log is what provides ACID.

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