Now, that would be inadvisable since many pets can be the same breed.Ī surrogate key is a generated unique identifier with no additional meaning. For example, if you used a dogs breed as the primary key for the Pets table. Natural keys are associated with a business context. Primary keys can have either natural or surrogate key values. Because these two values are the same, now the Pets and Pet Owners can be connected with a join statement. The Pet Owners table creates a foreign key, pet_id, that is refers is the same value as id in the Pets table. In the relationship diagram above, id in the Pets table is the primary key. This primary/foreign key relationship is the glue that ties relational tables together. In the next section, I cover how to create a primary key in Postgres.Ī foreign key is a value in a second table that references the primary key for the first table. By placing a PRIMARY KEY constraint on a specific column in a table, the database engine will guarantee that no row can be entered with the same key as an existing row. Primary keys uniquely identify rows in a table. There are two types of keys in SQL: primary and foreign. These databases receive the “relational” qualifier because “related” tables are connected together by keys. In its simplest form, the relational data model is a collection of tables containing rows of data. Relational databases have been around for almost 50 years. In this article, I’ll discuss why primary keys are important, different types of keys you can use, and a primary key with values that are guaranteed to have never, ever been used in the entire universe (with a 1/10^37 chance of error). Because of its importance, we have to give special consideration to how we select our primary keys. The foundation for a table in a relational database is the primary key. Relational databases are highly intertwined, so one small change can have unexpected, cascading effects. Note also that the example uuid (classic form) given in the OP doesn't appear to correspond to the example base64 string given (just using ).Changing the schema for large relational databases costs companies millions of dollars every year. Do the funny string transformations in the app layer.Īs for sending a base64 string into the db and then comparing it against stored uuid types, that is a conversion question already answered and explained here select substring(decode('pEUh0A+4St6AAjOFVFwzGA=','base64')::text from 3)::uuid Note that this does not change the uuid itself and you still should not be storing your uuid as text (or bytea, or anything "clever") for that matter. If you really, really want your database to do the legwork of base64 encoding your uuid, you can use the functions encode and uuid_send (undocumented) as seen here select encode(uuid_send('a44521d0-0fb8-4ade-8002-3385545c3318'::uuid),'base64') PostgreSQL also accepts the following alternative forms for input: use of upper-case digits, the standard format surrounded by braces, omitting some or all hyphens, adding a hyphen after any group of four digits. On the docs page, you will find the sampling of default permissible input string formats for ad-hoc work. Use the uuid datatype for database work with uuids handle special text formatting as near to the client as you can. would it make sense to save these short IDs directly as text in the database? Similarly the hexadecimal string you read in your client is also not the uuid - it is that same text representation of the uuid. It is just the text representation of the uuid. The text you pass to the database from your client (psql or pgAdmin for example) is not the uuid.
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