My past work in Microsoft SQL Server and Postgre environments.
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The Basics.sql file contains function like CREATE TABLE, INSER INTO+VALUES, SELECT+FROM, WHERE, GROUP BY+ORDER BY statements.
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In Intermediate.sql file, I played with functions like INNER/OUTER JOIN, UNION (ALL) operator, CASE WHEN statement, HAVING clause, UPDATING/DELETING, ALIASING, and PARTITION BY.
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In Advanced.sql file, I played with Common Table Expression (CTE), Temp tables, String functions, Stored procedures, and Subqueries.
Reference:
- Alex the Analyst SQL Tutorials
- SQL Cheat Sheet- Postgre. https://towardsdatascience.com/sql-cheat-sheet-776f8e3189fa?gi=dcb14aa9a054
- W3 School. https://www.w3schools.com/sql/default.asp