In this section, you learned how to construct different SELECT queries in SQL.
The first part that you saw with SQL is how to select data from tables. You saw how to connect to a database and query basic data from a table using column names or the wildcard parameter *.
After looking at basic SELECT statements, you then saw how to filter your selections using the WHERE clause.
Along with filtering, you also saw how to order your query selections. To do this, you use the ORDER BY clause. Remember that the default behavior there is to return results in ascending order. You can verbosely specify this with the ASC keyword, or modify the behavior to sort in descending order with the DESC keyword.
Next up, you saw how to create aggregates with your data. This involved using the GROUP BY statement. You saw that you can both explicitly state the column names that you wish to group by or that you can use aliases for the columns using numbers such as 1,2,3. You also got to investigate some aggregate functions such as COUNT(), MAX(), MIN(), and AVG(). Finally, you also saw that you can filter based on the results of aggregate functions using the HAVING clause.
After taking a look at more complex queries for a single table, you started to investigate how you could combine data from multiple tables. You did this using the JOIN clause. Remember that you can specify the links between tables with the USING() clause if the column name is identical between the tables or the ON clause if you must specify the link more manually. You also saw how to alias table names during your joins.
With some of the more complicated join and aggregate scenarios that began to arise, you also saw how to use subqueries to break down complex queries into parts. You also saw how you could potentially create aggregates of aggregates using subqueries.
Wrapping up the section, you saw how to create databases, tables, and subsequently populate those containers with data. You also saw how to delete or modify information. Database administration is a complex topic that has a lot more considerations including user permissions and improving query execution time, but this was a solid introduction to get you up and running.
Congratulations! You should have a good amount of SQL skills to harness in your data adventures going forward! While you are apt to use other tools such as Pandas to do a lot of your exploratory analysis and data manipulation, databases provide a much more powerful data storage option then flat files like csv or excel workbooks.