Join the query madness!
Of course, SQL does not stop with the the three keywords SELECT, FROM and WHERE. Another very often used keyword is JOIN, and more specifically INNER JOIN. Take this call for example:
SELECT name, post
FROM users INNER JOIN tweats on users.id = user_id
WHERE date > "2015-09-19"
Here, the users table is joined with the tweats table. This is possible because the id column in the users table corresponds to the user_id column in the tweats table. Also notice how name, from the users table, and post and date, from the tweats table, can be referenced to without problems.
Can you predict the outcome of the following query?
SELECT post, message
FROM tweats INNER JOIN comments on tweats.id = tweat_id
WHERE tweat_id = 77
A connection to the tweater database is already available as con; feel free to experiment!
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Intermediate Importing Data in R
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