"how to store a list in a column of a database table" Code Answer


no, there is no "better" way to store a sequence of items in a single column. relational databases are designed specifically to store one value per row/column combination. in order to store more than one value, you must serialize your list into a single value for storage, then deserialize it upon retrieval. there is no other way to do what you're talking about (because what you're talking about is a bad idea that should, in general, never be done).

i understand that you think it's silly to create another table to store that list, but this is exactly what relational databases do. you're fighting an uphill battle and violating one of the most basic principles of relational database design for no good reason. since you state that you're just learning sql, i would strongly advise you to avoid this idea and stick with the practices recommended to you by more seasoned sql developers.

the principle you're violating is called first normal form, which is the first step in database normalization.

at the risk of oversimplifying things, database normalization is the process of defining your database based upon what the data is, so that you can write sensible, consistent queries against it and be able to maintain it easily. normalization is designed to limit logical inconsistencies and corruption in your data, and there are a lot of levels to it. the wikipedia article on database normalization is actually pretty good.

basically, the first rule (or form) of normalization states that your table must represent a relation. this means that:

  • you must be able to differentiate one row from any other row (in other words, you table must have something that can serve as a primary key. this also means that no row should be duplicated.
  • any ordering of the data must be defined by the data, not by the physical ordering of the rows (sql is based upon the idea of a set, meaning that the only ordering you should rely on is that which you explicitly define in your query)
  • every row/column intersection must contain one and only one value

the last point is obviously the salient point here. sql is designed to store your sets for you, not to provide you with a "bucket" for you to store a set yourself. yes, it's possible to do. no, the world won't end. you have, however, already crippled yourself in understanding sql and the best practices that go along with it by immediately jumping into using an orm. linq to sql is fantastic, just like graphing calculators are. in the same vein, however, they should not be used as a substitute for knowing how the processes they employ actually work.

your list may be entirely "atomic" now, and that may not change for this project. but you will, however, get into the habit of doing similar things in other projects, and you'll eventually (likely quickly) run into a scenario where you're now fitting your quick-n-easy list-in-a-column approach where it is wholly inappropriate. there is not much additional work in creating the correct table for what you're trying to store, and you won't be derided by other sql developers when they see your database design. besides, linq to sql is going to see your relation and give you the proper object-oriented interface to your list automatically. why would you give up the convenience offered to you by the orm so that you can perform nonstandard and ill-advised database hackery?

By kervin on September 29 2022

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