SQL query to a relational algebra

[Kratik]

I need to translate the SQL query to a relational algebra expression. 

SELECT P.Name 
FROM Players P, Games G
WHERE P.Id =  G.PlayerId
    AND P.Game = 'Football' AND G.Season ='2019'

where: Players (Id, Name, Game) Games (PlayerId, GameCode, Season)

[jhonson]

I think this might help you with relational algebra expression for the given SQL query is:

• π Name (Players ÷⋈ Id=PlayerId ((Players ⨝ Games)
• ⨝ (Game = 'Football' AND Season = '2019')))

Explanation:

• π Name: Projection to get only the "Name" attribute.
• Players ÷⋈ Id=PlayerId: Natural Join between Players and Games on "Id" and "PlayerId".
• Players ⨝ Games: Cartesian product of Players and Games.
• (Game = 'Football' AND Season = '2019'): Selection to get only the tuples with "Game" equal to "Football" and "Season" equal to "2019".