Introduction to SQL
Which of the following query finds the name of the sailors who have reserved at least two boats?

SELECT DISTINCT s.sname FROM sailors s, reserves r1, reserves r2 WHERE s.sid = r1.sid AND r1.sid = r2.sid AND r1.bid ≠ r2.bid
All of these
SELECT DISTINCT s.sname FROM sailors s, reserves r1, reserves r2 WHERE s.sid = r1.sid AND COUNT(r1.bid) > r2.bid
SELECT DISTINCT s.sname FROM sailors s, reserves r1, reserves r2 WHERE s.sid = r1.sid AND r1.sid = r2.sid AND r1.bid <> r2.bid

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Introduction to SQL
To define what columns should be displayed in an SQL SELECT statement:

use USING to name the source table(s) and list the columns to be shown after SELECT.
use USING to name the source table(s) and list the columns to be shown after WHER
use FROM to name the source table(s) and list the columns to be shown after SELECT.
use SELECT to name the source table(s) and list the columns to be shown after USING.

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Introduction to SQL
What is a view?

A view is a database diagram.
None of these
A view is a virtual table which results of executing a pre-compiled query. A view is not part of the physical database schema, while the regular tables are.
A view is a special stored procedure executed when certain event occurs.

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