iframe-proxy | Sunbelt Computer Software

57 lines (47 loc) · 2.21 KB

-- All of these JOINs requires more than two tables.
-- Remember: then using the JOIN keyword it doesn't matter what order we join
-- the tables in.  That is,
--   SELECT * FROM TableA JOIN TableB ON (TableA.id = TableB.table_a_id)
-- is the same as
--   SELECT * FROM TableB JOIN TableA ON (TableA.id = TableB.table_a_id)
-- Also remember: the syntax TableA.first_name means the "first_name" field
-- from the table named TableA.  Field names have to be unique in a given table.
-- That is, you can't have two fields / columns named "first_name" in the same
-- However, two *different* tables can both have a "first_name" field. For
-- example, you might have a "customers" table and an "employees" table, both
-- of which have "first_name", "last_name", and "email" fields.  If you have
-- a query that involves *both* customers and employees, you'll need to refer
-- to fields using their table name, i.e., customers.first_name,
-- employees.first_name, customers.email, and so on.
-- Remember, the "skeleton" for a SELECT query with JOINs looks like
--   SELECT <field names>
--   FROM <table1>
--   JOIN <table2>
--     ON (<join condition>)
--   JOIN <table3>
--     ON (<join condition>)
--   WHERE <filtering clauses>
--   GROUP BY / ORDER BY / LIMIT / etc.
-- This is the general order, but a SELECT query *always* needs a FROM clause.
-- Exercises
-- What are the five highest grossing hip hop tracks?
-- What are the 3 least frequently-purchased tv shows?
-- What are the 5 highest-grossing genres?
-- Who are the 5 artists with the longest average track length?
-- Write a query that sorts a specific album's tracks by sales volume (you'll have to pick an arbitrary album title)
--   e.g., "Give me the the tracks from Alanis Morissette's Jagged Little Pilled sorted by sales volume"
-- Write a query that sorts a specific album's tracks by gross sales (you'll have to pick an arbitrary album title)
-- How would you handle the case where two different artists have albums with the same name?
--   e.g., sometimes both Peter Gabriel's first album and Led Zeppelin's first album are referred to as "One" or "I"
-- We're runnin' low on queries!  Come up with 3-5 of your own and write them.

Sunbelt Computer Software

PL/B Language Development and Support

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Sunbelt Computer Software

PL/B Language Development and Support

Uh oh!

FilesExpand file tree

multi_join.sql

Latest commit

History

multi_join.sql

File metadata and controls