primary key and represents a unique Event. The "elD"

in Games is a foreign key referencing elD from

Events.

"pID" in Players is a simplification of the primary key

and represents a unique player. The Name column in

Players is still required to be unique, as an additional

candidate key.

"wpID" and "bpID" in Games represent white players

and black players, respectively, and they are foreign

keys referencing pID from Players. Hint: you can't

natural join Games with Players because they have

no columns with the same name.

Recall that in this database, a result of $"$W$"$ means

white won, $"$B$"$ means black won, and $"$D$"$ means it

was a draw.

Note that the instance data given is just to show an

example, and it may change $($you can't query by

instance$).$

Events

Players

Games

Write relational algebra queries for the following. You

can $($and should$)$ write your queries on multiple lines,

if appropriate, using the renaming operator.

Find the names of any player with an Elo rating

of $2850$ or higher.

Find the names of any player who has ever

played a game as white.

Find the names of any player who has ever won

a game as white.

Find the names of any player who played any

games in $2018.$

Find the names and dates of any event in which

Magnus Carlsen lost a game.

Find the names of all opponents of Magnus

Carlsen. An opponent is someone who he has

played a game against. Hint: Both Magnus and

his opponents could play as white or black.

Find the names of all players who have never

lost a game $($a draw is not considered a loss$).$