Database SQL questiions and fill in the blanks. a. If attribute \"student_id\" i

Question

Database SQL questiions and fill in the blanks.

a. If attribute "student_id" is the primary key of a table, then no two ____ of the table can have the same value of _____.

b. The value of a programming language variable is to a relation instance as the type of a programming language variable is to a _____________.

c. Can a relation schema has attributes {a, b, c, d, e}. If {a,b} is a candidate key for the schema, then is {a, b, d} also a candidate key? (yes or no). ______.

d. Every operartion of relation algebra produces _________ as output.

e. Using the non-Greek notation write the following SQL statment as an expression in relation algebra: " select age from census where workclass = 'Private"; " ________________________.   

Explanation / Answer

a. If attribute "student_id" is the primary key of a table, then no two rows of the table can have the same value of student_id.

b. The value of a programming language variable is to a relation instance as the type of a programming language variable is to a attribute.

c. Can a relation schema has attributes {a, b, c, d, e}. If {a,b} is a candidate key for the schema, then is {a, b, d} also a candidate key? (yes or no). no.

d. Every operartion of relation algebra produces instances of relation as output.
e. Using the non-Greek notation write the following SQL statment as an expression in relation algebra: " select age from census where workclass = 'Private"; " {< age > | census workclass = 'Private'}   

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