INSERT and primary key uniqueness violations
In many relational databases, if you try to insert a row that has already been inserted, the operation can fail because the primary key gets duplicated. Impala, however, does not fail the query. Instead, it generates a warning and continues to execute the remainder of the insert statement.
The current value of the row is now
INSERT INTO my_first_table VALUES (99, "sarah"); UPSERT INTO my_first_table VALUES (99, "zoe");