Variant data type

Mark Needham

Learn about the new Variant data type in ClickHouse 25.3, which allows storing multiple data types in a single column. This tutorial covers everything from basic usage to advanced schema inference techniques for handling heterogeneous data.

• Create and cast values to variant types with multiple union types
• Use the variantType() function to determine which type is being used for each value
• Handle arrays with mixed data types using the use_variant_as_common_type setting
• Access underlying values with dot notation syntax (value.uint8, value.string)
• Apply variant types to CSV file ingestion with schema inference hints
• Understand limitations when using variant types as sorting keys