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PostgreSQL learning

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Software ==>	Postgres SQL (35 exercises)
Topic ==>	Derived tables and CTEs (3 exercises)
Level ==>	Average difficulty
Subject ==>	PostgreSQL training

Use a CTE to aggregate information about tracks on albums without multiple GROUP BY columns

This exercise is provided to allow potential course delegates to choose the correct Wise Owl Microsoft training course, and may not be reproduced in whole or in part in any format without the prior written consent of Wise Owl.

If you don't have a copy of the music_01 database, first follow the instructions at the following link to create it: https://www.wiseowl.co.uk/postgres/exercises/postgres-sql/using-postgres/5350/

The aim of the exercise is to create this query:

Query with grouped fields boxed

We want to group by these 3 columns from the album table, but it's tedious having to list them all in the GROUP BY clause of your query just so we can display their values.

Start by creating a query which groups rows in the Track table by the Album_ID, creating the aggregated values shown below:

Aggregated data by album id

Note that the only album details you need to include are the album id - the rest we can look up in the second part of our query.

Convert this query into a common table expression and join it to the album table to show the following results:

Final stats by album

The final query sorts the tracks by the average track length.

Save the script as Also much simpler.sql and then close it.

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