Primary Key
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What is Primary Key?
A primary key in SQL is a unique identifier for each record in a database table. It ensures that each row in the table is uniquely identifiable, meaning no two rows can have the same primary key value. A primary key is composed of one or more columns, and it must contain unique values without any NULL entries. The primary key enforces entity integrity by preventing duplicate records and ensuring that each record can be precisely located and referenced, often through foreign key relationships in other tables. Using a primary key is fundamental for establishing relationships between tables and maintaining the integrity of the data model.
Free resources to learn Primary Key
- ArticleSQL Primary Key
More in stage 5: Aggregate Queries
Primary Key: common questions
Can I learn Primary Key in Hindi?
This lesson is written in English. Once you sign in, open it in the interactive course and ask the AI tutor to explain Primary Key in Hindi or Hinglish. The tutor answers from this lesson’s own text, so it stays on the syllabus, and it runs on your own Google, OpenAI or Anthropic key.
Is this Primary Key tutorial for beginners?
It is lesson 37 of 112 in the free SQL roadmap, in stage 5, Aggregate Queries. If you are new to SQL, start from stage 1 and come back here in order; if you already know the earlier stages, this lesson stands on its own.