Re: Expressing SQL in relational algebra
From: Neo <neo55592_at_hotmail.com>
Date: 15 Mar 2003 20:23:05 -0800
Message-ID: <4b45d3ad.0303152023.2e117071_at_posting.google.com>
Date: 15 Mar 2003 20:23:05 -0800
Message-ID: <4b45d3ad.0303152023.2e117071_at_posting.google.com>
> > "SELECT * FROM T_Person WHERE (age=20) AND (weight=180);" in rel algebra?
>
> (T_Person | age=Years(20) AND weight=Pounds(180)),
> RESTRICT(T_Person,age=Years(20) AND weight=Pounds(180)),
> or T_Person WHERE ( age=Years(20) AND weight=Pounds(180) )
Could the above also be expressed as "person ^ age ^ 20 ^ years ^ weight ^ 180 ^ pounds" where ^ means AND?
How does Tutorial-D express joins such as: "SELECT * FROM T_Car JOIN T_Part ON T_Car.ID = T_Part.CarID WHERE T_Part.Color = 'red'"; Received on Sun Mar 16 2003 - 05:23:05 CET