Question

An analyst writes a SQL query to combine a Customers table (500 rows) with an Orders table (2,000 rows), expecting roughly 2,000 result rows. Instead, the query returns 1,000,000 rows and runs extremely slowly. Reviewing the query, the analyst notices there is no ON condition linking the two tables. What most likely happened?

Accepted Answer

The join produced a Cartesian product because no join condition was specified, multiplying every row in one table by every row in the other

Answer

The query performed a left outer join that duplicated unmatched customer records

Answer

The Orders table contained duplicate primary keys that inflated the row count

Answer

The database automatically applied a union that stacked all rows from both tables