How to DROP TABLE in ClickHouse

Galaxy Glossary

How do you safely drop a table in ClickHouse?

DROP TABLE permanently removes a table and its data from a ClickHouse database.

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Description

Example H2

Example H3

Why use DROP TABLE in ClickHouse?

DROP TABLE instantly deletes the table structure and all stored data, freeing disk space and preventing further queries on the table. Use it when a table is obsolete or recreated elsewhere.

What is the basic syntax?

Write DROP TABLE [IF EXISTS] [db.]table_name [ON CLUSTER cluster_name] [NO DELAY]. Add IF EXISTS to avoid errors if the table is missing.Use ON CLUSTER to drop tables across a cluster.

How do I drop a table safely?

Wrap the command in a transaction-safe environment or back up data first. In production, combine IF EXISTS and run during low-traffic windows.

Can I drop distributed and local tables together?

Yes. Execute DROP commands for both the distributed and underlying local tables. Use ON CLUSTER to ensure consistency across shards.

Example workflow

1) Stop writes to Orders. 2) Back up recent partitions.3) Run DROP TABLE IF EXISTS Orders ON CLUSTER company_cluster. 4) Verify with SHOW TABLES.

Best practices?

Always qualify the database (e.g., analytics.Orders) to avoid dropping similarly named tables in other DBs. Maintain a change log for auditing.

What happens to dependent views?

DROP TABLE fails if materialized views depend on it. Drop or detach the views first, or use DETACH TABLE to keep metadata while removing data.

How to reverse a mistaken drop?

Recovery requires restoring from backup or replicated replicas.ClickHouse lacks an inherent UNDO, reinforcing the need for backups.

Why How to DROP TABLE in ClickHouse is important

How to DROP TABLE in ClickHouse Example Usage


-- Remove an outdated staging table in the ecommerce warehouse
DROP TABLE IF EXISTS staging.OrderItems ON CLUSTER company_cluster;

How to DROP TABLE in ClickHouse Syntax


DROP TABLE [IF EXISTS] [database.]table_name [ON CLUSTER cluster_name] [NO DELAY];

-- Ecommerce examples
-- 1. Drop obsolete sandbox table
DROP TABLE IF EXISTS sandbox_temp_orders;

-- 2. Drop Orders table across cluster
DROP TABLE analytics.Orders ON CLUSTER company_cluster;

-- 3. Drop replicated Products table without delay
DROP TABLE IF EXISTS Products NO DELAY;

Common Mistakes

Omitting the database qualifier leads to dropping a table in the current DB instead of the intended one. Always specify <code>db.table</code>.
Forgetting to drop dependent materialized views causes an error. Drop or detach the views before the table.