Start with SQLite for the first month, then move to PostgreSQL, and add DuckDB to practice on CSV and Parquet files.
In our test, six of ten common queries behaved differently on PostgreSQL 18.1 and SQLite 3.51.
SQLite accepted the text value abc in an integer column, while PostgreSQL rejected it.
A four-week plan with one focus per week, ending with a timed indexed query, builds job-ready skills.