Two tables with 100 rows each with arbitrary numbers. What is the minimum and maximum number of rows that FULL OUTER JOIN can return?

Suppose there are two tables A and B, each with 100 rows with arbitrary numbers.

• Minimum number of rows in the result of a FULL OUTER JOIN:

  Minimum — 100 rows, if all values in both tables match by key (i.e., each row from A corresponds to a row from B).

• Maximum number of rows:

  Maximum — 200 rows, if there are no matching key values between the tables. Then the result contains all 100 rows from A and all 100 rows from B, without merging.

Thus, the result of a FULL OUTER JOIN can contain from 100 to 200 rows in this case.