Joins and double counting

When Nexatron can tell that a join repeats rows

Nexatron checks totals and counts across joins for double counting. It knows a join can repeat rows when the relationship is declared or certified, or when your connection's latest exact profile shows the joined column repeating values (fewer distinct values than rows). Profiles are taken during onboarding; exact profiles are available for PostgreSQL, Redshift, MySQL / MariaDB, SQL Server and DuckDB.

Limitation

On a connection whose tables have not been profiled yet (or whose profile is unavailable or approximate), Nexatron cannot tell from the warehouse alone whether a join repeats rows. Declare or certify the relationship, or let profiling finish, so totals and counts across joins can be checked.