A unique identifier for each row in a database table, like a student ID number.
A primary key is a column (or columns) that uniquely identifies each row in a table. No two rows can have the same primary key value. Primary keys are required for databases to function—they allow you to reference specific rows and update/delete precisely.
Common primary keys are IDs (numeric or UUID), email addresses, or usernames. The database enforces uniqueness—it will not let you insert a duplicate. Primary keys are also the fastest way to look up rows. You define them using SQL CREATE TABLE statements.
Every table should have a primary key. When you create a table, you explicitly mark one column (or combination of columns) as PRIMARY KEY. Other tables reference this with foreign keys.
In modern databases like Supabase, primary keys are typically UUIDs — long random strings that are globally unique and more secure than auto-incrementing numbers.
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