database week1/jianxin #148
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| -- Find all the tasks that are marked as done | ||
| SELECT * FROM task | ||
| WHERE status_id IN (SELECT id FROM status WHERE name LIKE "%done%"); |
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This does not block the review because your query works, but I still suggest you follow this advice to get more clear and meaningful code.
You use IN when there is a list of possible values. Although it works in this case, there is only one status for "Done", so you could do SELECT * FROM task WHERE status_id = (...) and this statement would be a bit more clear.
Similarly, in the subquery you are searching for statuses whose name contain done. There is only one status for "Done", so you could do SELECT id FROM status WHERe name = 'Done', which again is a bit more clear.
| -- Get the title and status (as text) of all tasks | ||
| SELECT task.title AS task_title, status.name AS task_status | ||
| FROM task | ||
| LEFT JOIN status on task.status_id = status.id; |
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The column status_id in the table task cannot be null (this can be checked in the CREATE TABLE statement here). This means that this LEFT JOIN is no different from an INNER JOIN or JOIN (which is the same as an INNER JOIN).
This doesn't block the review either, but I suggest that you use LEFT or RIGHT joins only when they make a difference from an INNER, i.e.: when the column you are joining on can be null.
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