Introduction to Database Systems Queries in SQL The select ...
Introduction to Database Systems Queries in SQL The select ...
Introduction to Database Systems Queries in SQL The select ...
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Exercise 3: Solution<br />
“<strong>The</strong> fathers of persons who earn more than 20K”<br />
π father (FatherChild<br />
child=name σ <strong>in</strong>come>20 (Person))<br />
<strong>select</strong> dist<strong>in</strong>ct fc.father<br />
from person p, fatherChild fc<br />
where fc.child = p.name<br />
and p.<strong>in</strong>come > 20<br />
27<br />
Exercise 4: Jo<strong>in</strong><br />
“Father and mother of every person”<br />
Write the query both <strong>in</strong> relational algebra and <strong>SQL</strong><br />
28
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