Database Interview
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Answer these questions using your knowledge of SQL, Relational Database Management Systems (e.g. MySQL, SQL Server, Oracle, etc.) and the sample table below.
| Colors | |
|---|---|
| id | color |
| 1 | Red |
| 2 | Blue |
| 3 | Red |
| 4 | Green |
| 5 | Blue |
| 6 | Red |
| 7 | Orange |
A.
Write a query to count the number of times each color appears in the table Colors. Your output should look like this:
| color | count |
|---|---|
| Blue | 2 |
| Green | 1 |
| Orange | 1 |
| Red | 3 |
B.
Write a query to list the the colors in the table Colors. The output of the query should look like this:
| unique colors |
|---|
| Blue |
| Green |
| Orange |
| Red |
C.
Which type of sub query can be evaluated independently?
- correlated
- uncorrelated