Quick Check 4.7 – Data 100, Summer 2020

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Which of the following are true? *

The query SELECT * from t LIMIT 5; produces a simple random sample.

The query SELECT * from t ORDER BY RANDOM() LIMIT 5; produces a simple random sample.

In most scenarios, subqueries and common table expressions are interchangeable.

Subqueries can only be used in the FROM clause.

Subqueries can only be used in both the FROM and WHERE clauses.

Required

(Spring 2019 Midterm 1) For the following question consider the following tables. The cities table contains one row per city and its population in thousands. The names table contains one row per state. The states table contains one row per state with its population in millions. Assume that cities contains only a small subset of US cities. There may be multiple cities in each state, but every city is in a state that appears in both names and states, and every state contains at least one city.

Suppose we have a table t that is the same as cities but with an additional column ab containing the abbreviation (e.g. CA) of the state in which each city is located. Fill in the blank in the following query to create a two-column table u of the cities and their populations (labeled city and pop) that are in states with a population above 5 million.

CREATE TABLE u AS SELECT city, pop FROM t WHERE ab IN (_______________________); *

SELECT * FROM states

SELECT state FROM states

SELECT * FROM states WHERE people > 5

SELECT state FROM states WHERE people > 5

For the following question consider the following tables:

What is the output of the following query? *

Popeye

Bob

Jack Sparrow

Garfield

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