How does ClickHouse find the relationship between columns?

ClickHouse does not store explicit relationships between columns, as it is a columnar analytical database designed for fast data reading and aggregation.

Relationships between columns in ClickHouse are determined at the query and table schema level:

• In ClickHouse tables, columns are stored separately but logically connected as parts of a single row.
• To combine data from different tables (for example, by key), SQL JOINs are used, where the relationship is determined by the values of key columns.
• ClickHouse does not support foreign keys or integrity constraints, so the relationship between columns is the responsibility of the user and query logic.

Thus, "relationship between columns" is a concept at the schema and query level, not an inherent mechanism of ClickHouse. It relies on column names and their values for data joining and filtering.