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Mit SQL spricht man mit relationalen Datenbanken. Ziele Verstehe die folgenden SQL Befehle SELECT WHERE ORDER INNER JOIN, LEFT JOIN GROUP BY LIMIT UPDATE INSERT and INSERT...

DELETE

...welchen Umständen kann hot_standby_feedback zu Problemen mit VACUUM und Indizes führen? Inhalte SQLZOO Tutorial: Übungsaufgaben in Tutorials Joins Visualizer: Explains the differences between various types of JOIN statements...

Understand that an expression like User.where(email: 'foo@bar.com') does not make an SQL query. It simply returns a scope object for further chaining with #where, #order, etc.

...will make an SQL query when you use them like an array, e.g. by iterating over them with #each. This may cause the scope to accidentally load its results prematurely...