A Note on Range Variables

• Really needed only if the same relation appears twice in the FROM clause. The previous query can also be written as:

SELECT S.sname

FROM Sailors S, Reserves R

WHERE S.sid=R.sid AND bid=103

SELECT sname

FROM Sailors, Reserves

WHERE Sailors.sid=Reserves.sid

AND bid=103

It is good style,

however, to use

range variables

always!

OR

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