306 Chapter 10 Figure 10-30 refines (Free web hosting music) relationships between
306 Chapter 10 Figure 10-30 refines relationships between tables as identifying, non-identifying, and NULL valued. The INSTRUMENT table contains a hierarchy, with instruments divided into sections (such as a strings section, or a percussion section). The GENRE table also contains a hierarchy of genres and sub-genres. For example, hard rock music is part of rock music, and rock music is part of modern music. Hard rock music could contain sub-genres as well, such as alternative rock. The INSTRUMENT and GENRE table has self join or fishhook join relationships added, to represent the hierarchies. A musician must play at least one instrument (voice is an instrument). Skills cannot exist without a musician. Figure 10-30: Refining relationships as identifying, non-identifying, and NULL valued. Instrument section_id (FK) instrument instrument_id Skill musician_id (FK) skill Genre parent_id (FK) genre genre_id Musician instrument_id (FK) band_id (FK) name phone email musician_id Band genre_id (FK) name members founding_date band_id Discography band_id (FK) cd_name release_date price discography_id Merchandise band_id (FK) type price merchandise_id Show band_id (FK) location address directions phone show_date show_times show_id Advertisement band_id (FK) musician_id (FK) ad_date ad_text phone email requirements advertisement_id
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