merge - ClickHouse Documentation

Creates a temporary Merge table. The table schema is derived from underlying tables by using a union of their columns and by deriving common types. The same virtual columns are available as for the Merge table engine.

Syntax

merge(['db_name',] 'tables_regexp')

Arguments

Argument	Description
`db_name`	Possible values (optional, default is `currentDatabase()`): - database name, - constant expression that returns a string with a database name, for example, `currentDatabase()`, - `REGEXP(expression)`, where `expression` is a regular expression to match the DB names.
`tables_regexp`	A regular expression to match the table names in the specified DB or DBs.

Merge table engine

Last modified on June 23, 2026

mergeTreeIndexRepresents the contents of index and marks files of MergeTree tables. It can be used for introspection.

​Syntax

​Arguments

​Related

Syntax

Arguments

Related