# Misgivings (or misconceptions?) about class=table concept **URL:** \ **Category:** Rails\ **Created:** [May 20, 2009, 6:53pm UTC](https://www.ruby-forum.com/t/misgivings-or-misconceptions-about-class-table-concept/168425 "2009-05-20T18:53:47Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![mk27](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mk27](https://www.ruby-forum.com/u/mk27)\ **Post date:** [May 20, 2009, 6:53pm UTC](https://www.ruby-forum.com/t/misgivings-or-misconceptions-about-class-table-concept/168425/1 "2009-05-20T18:53:47Z")
Please bear with me as I am totally new to Rails AND sql. Let’s say a want a database & application for a record collection (using sql and rails). If I want the database to contain information down to the length of a song, how can I implement this using the class = table model? For example, the way I have the db now, ignoring rails, is a table “of Contents” listing all artists (one column). Each artist then has a table listing all their albums, several columns since we want the total length of the album and (since this is a digital catalog) a location where the actual album is stored. Then we need a table for each album listing each song, with the length. Going with the class=table model, that means I will be stuck with a separate class for every single artist and album, which is beyond ridiculous if not completely unworkable. But if I organize the material differently – eg, a table “artist” with a column “albums” (fine, if they were just objects) some single table cell would have to contain a list of all the albums. Slightly awkward, since each album will then have to be parsed out of a string of albums, but more realistic. Then I would have a table “albums” with columns/methods “artist” and “songs”. But when it comes down to including the length of each song, this methodology is gonna get dunder-headed. The former model makes much more sense anyway, from any perspective _except_ it would appear to be unworkable with rails. Clearly I am missing something here, I hope. Anyone want to offer me a clue? ---
**Author:** ![mk27](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mk27](https://www.ruby-forum.com/u/mk27)\ **Post date:** [May 20, 2009, 7:43pm UTC](https://www.ruby-forum.com/t/misgivings-or-misconceptions-about-class-table-concept/168425/2 "2009-05-20T19:43:09Z")
On May 20, 12:53 pm, Mk 27 [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > Please bear with me as I am totally new to Rails AND sql. > > Let’s say a want a database & application for a record collection (using > sql and rails). If I want the database to contain information down to > the length of a song, how can I implement this using the class = table > model? Very easily. Read on. > For example, the way I have the db now, ignoring rails, is a table “of > Contents” listing all artists (one column). Each artist then has a > table listing all their albums, So you’re saying you have table: Contents ±------------------+ | name | ±------------------+ | Michael J. | | Bruce Springsteen | table: Michael J. ±---------+ | album | ±---------+ | Thriller | table: Bruce Springsteen ±-------------------+ | album | ±-------------------+ | Working on a Dream | ? If that’s what you’re saying, then this is poor database design, with or without Rails. > several columns since we want the total > length of the album and (since this is a digital catalog) a location > where the actual album is stored. Then we need a table for each album > listing each song, with the length. No we don’t. Keep reading. > Going with the class=table model, that means I will be stuck with a > separate class for every single artist and album, which is beyond > ridiculous if not completely unworkable. But if I organize the material > differently – eg, a table “artist” with a column “albums” (fine, if > they were just objects) some single table cell would have to contain a > list of all the albums. Slightly awkward, since each album will then > have to be parsed out of a string of albums, but more realistic. Still no. Please learn about the proper use of foreign keys and the Third Normal Form. > Then I > would have a table “albums” with columns/methods “artist” and “songs”. > But when it comes down to including the length of each song, this > methodology is gonna get dunder-headed. > > The former model makes much more sense anyway, from any perspective > _except_ it would appear to be unworkable with rails. Clearly I am > missing something here, I hope. Anyone want to offer me a clue? The former model actually make _no_ sense, since it contains lots of tables with identical structure. That’s your cue to realize that they should be one table. What you want instead is something like this: table: artists ±—±------------------+ | id | name | ±—±------------------+ | 1 | Michael J. | | 2 | Bruce Springsteen | table: albums ±—±-------------------±----------+ | id | name | artist\_id | ±—±-------------------±----------+ | 1 | Working on a Dream | 2 | | 2 | Thriller | 1 | table: songs ±—±-------------±---------+ | id | name | album\_id | ±—±-------------±---------+ | 1 | Beat It | 2 | | 2 | Thriller | 2 | | 3 | Outlaw Pete | 1 | | 4 | My Lucky Day | 1 | Then use has\_many and belongs\_to properly and Rails will deal with creating the object graph. Does that make more sense? ## Best, Marnen Laibow-Koser removed\_email\_address@domain.invalid [http://www.marnen.org](http://www.marnen.org) ---
**Author:** ![mk27](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/5e9695/32.png) [@mk27](https://www.ruby-forum.com/u/mk27)\ **Post date:** [May 20, 2009, 7:58pm UTC](https://www.ruby-forum.com/t/misgivings-or-misconceptions-about-class-table-concept/168425/3 "2009-05-20T19:58:49Z")
Marnen Laibow-Koser wrote: > Does that make more sense? Yep. Thanks much.