12. Quiz: UNION

Appending Data via UNION

Write a query that uses UNION ALL on two instances (and selecting all columns) of the accounts table. Then inspect the results and answer the subsequent quiz.

Code

If you need a code on the https://github.com/udacity.

UNION vs. UNION ALL

Without rewriting and running the query, how many results would be returned if you used UNION instead of UNION ALL in the above query?
SOLUTION: 351

Pretreating Tables before doing a UNION

Add a WHERE clause to each of the tables that you unioned in the query above, filtering the first table where name equals Walmart and filtering the second table where name equals Disney. Inspect the results then answer the subsequent quiz.

Code

If you need a code on the https://github.com/udacity.

Alternative to UNION

How else could the above query results be generated?
SOLUTION: SELECT * FROM accounts WHERE name = 'Walmart' OR name = 'Disney'

Code

If you need a code on the https://github.com/udacity.

Performing Operations on a Combined Dataset

Perform the union in your first query (under the Appending Data via UNION header) in a common table expression and name it double_accounts. Then do a COUNT the number of times a name appears in the double_accounts table. If you do this correctly, your query results should have a count of 2 for each name.

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