The system table system.numbers is a virtual table that generates a series of consecutive integers starting from 0, suitable for generating test data or filling data.
Example
Query data:

SELECT * FROM system.numbers LIMIT 10;

Query results:

┌─number─┐ 
│      0 │ 
│      1 │ 
│      2 │ 
│      3 │ 
│      4 │ 
│      5 │ 
│      6 │ 
│      7 │ 
│      8 │ 
│      9 │ 
└────────┘