ClickHouse/docs/en/operations/system-tables/one.md

slug
/en/operations/system-tables/one

one

This table contains a single row with a single dummy UInt8 column containing the value 0.

This table is used if a SELECT query does not specify the FROM clause.

This is similar to the DUAL table found in other DBMSs.

Example

SELECT * FROM system.one LIMIT 10;

┌─dummy─┐
│     0 │
└───────┘

1 rows in set. Elapsed: 0.001 sec.