Question

Evaluate this SELECT statement:

SELECT p.player_id, m.last_name, m.first_name, t.team_name
FROM player p
LEFT OUTER JOIN player m ON (p.manager_id = m.player_id)
LEFT OUTER JOIN team t ON (p.team_id = t.team_id);
Which join is evaluated first?
a.The join between the player table and the team table on MANAGER_ID
b.The self-join of the player table
c.The join between the player table and the team table on TEAM_ID
d.The join between the player table and the team table on PLAYER_ID

Answer 1

The SELECT statement evaluates the self-join of the player table first, where it joins on the manager_id, following the order in which the joins appear in the query.

Step-by-step explanation:

To evaluate the given SELECT statement, we need to understand the order in which the SQL engine processes joins. The order is determined by the sequence the joins appear in the query rather than any inherent logic relating to the table names or key names. The first join that is evaluated in this statement is a self-join of the player table which aliases the first instance as 'p' and the second instance as 'm' to link players and their managers. This is followed by the join with the team table on the team_id column.

The correct answer is b. The self-join of the player table.