Outer joins can be left outer joins or can be right outer joins. In a left outer join, the query includes all of the rows from the first table in the SQL statement FROM clause, and only those rows from the other table where the joining field contains values common to both tables.
Rival \Rival\, v. t. [imp. & p. p. Rivaledor Rivalled; p. pr. & vb. n. Rivaling or Rivalling.] 1. To stand in competition with; to strive to gain some object in opposition to; as, to rival one in love. [1913 Webster] 2. To strive to equal or exel; to emulate.
An opponent is your competition, whether it's a rival hockey team, or the other finalist in the chess tournament. Coaches tell you to never underestimate your opponent. Someone who competes or fights against you is your opponent. If you're arguing that chocolate ice cream is better than vanilla, the vanilla ice cream fan is your opponent. An opponent can also be someone who opposes, like an opponent of gun control laws. The Latin word opponent means setting against, and it was first used in English to describe the person who would begin a certain type of philosophical debate.