Question

(a) What are the operations that correspond to the query expressed using this SQL statement?

SELECT Supplier

FROM Part_needs

WHERE \(1000 \le \)Part_number\( \le 5000\).

(b) What is the output of this query given the database in Table 9 as input?

Short answer

(a) The part needs dataset.

(b) The output is 23,31,33.

Step-by-step solution

Define Sets

The collection of the number of elements is define as set. The set is denoted by a variable that has number of elements inside the brackets. Also, the change in order or the repletion of the elements makes no change in the complete set.

Determine the operation corresponding the query

(a)

The first line "SELECT Supplier" means that they are interested in the attribute Supplier.

The second line "FROM Part needs" means that it is needed to use the "Part needs" data set, which is called the relation \(R\).

Note that "Supplier" is the lst column in the "Part needs" data set (table 9).

This then means that the SQL statement will give the projection \({P_1}\) of the dataset \(R\): \({P_1}(R)\).

The third line "WHERE \(1000 \le \) Part number \( \le 5000\)" means that the only want is supplier information for those \(n\)-tuples that satisfy the condition.

Determine the output of the query

(b)

First remove the rows in table 9 that do not satisfy the condition:

\(\begin{array}{*{20}{c}}{{\rm{ Supplier }}}&{{\rm{Par}}{{\rm{t}}_{\rm{n}}}{\rm{umber}}}&{{\rm{ Project }}}\\{23}&{1092}&1\\{23}&{1101}&3\\{31}&{4975}&3\\{31}&{3477}&2\\{33}&{1001}&1\end{array}\)

Next restrict the data set to only include the "Supplier" data:

Supplier

23

23

31

31

33

Remove the repetitions:

Supplier

23

31

33

The output of the query then contains all \(n\)-tuples in the above table: 23,31,33.