Qualified Column Names

Why it matters

This feature was created to resolve ambiguities in queries involving multiple tables or subqueries with overlapping column names. By enabling qualified column names, users can specify which table a column belongs to, preventing errors and improving query clarity and maintainability.

How to use it

Use qualified column names by prefixing the column name with the table name or alias, separated by a dot. For example, table_name.column_name or alias.column_name. This explicit qualification helps ClickHouse parse and execute queries that have columns with the same name coming from different tables or subqueries.