Primary Key

Easy — everyone uses thisDatabase

ELI5 — The Vibe Check

A primary key is the unique ID that every row in a table must have. Like a social security number for your data — no two rows can have the same one. It is how the database knows exactly which row you mean when you say 'give me user 42'.

Real Talk

A primary key is a column or set of columns that uniquely identifies each row in a table. It enforces the UNIQUE and NOT NULL constraints automatically. Every table should have a primary key. Common types are auto-incrementing integers (SERIAL) and UUIDs.

Show Me The Code

CREATE TABLE orders (
  id SERIAL PRIMARY KEY,  -- auto-increments
  user_id INT NOT NULL,
  total DECIMAL(10,2)
);

When You'll Hear This

"Always include a primary key on every table." / "The id column is the primary key."

Related Terms

Auto Increment

Auto increment means the database assigns the next ID number automatically every time you insert a row.

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Foreign Key

A foreign key is how you link two tables together. If an 'orders' table has a 'user_id' column pointing to the 'users' table, that is a foreign key.

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Index

A database index is like the index in the back of a book. Without it, the database reads every single row to find what you want.

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Table

A database table is exactly like a spreadsheet tab. It has columns across the top (name, email, age) and rows going down (one per person).

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UUID (Universally Unique Identifier)

A UUID is a randomly generated ID that looks like 'a3b4c5d6-...' and is practically guaranteed to be unique across the entire universe.

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