📝[Docs]: add sql documentation (primary key , foreign key and constraints in detail )

[dinesh-2047]

Is there an existing issue for this?

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Issue Description

The documentation currently lacks detailed explanations for some core SQL concepts.
This issue aims to improve the database-related documentation by adding comprehensive details about:

Primary Key — Definition, purpose, and usage examples

Foreign Key — How it works, relationships between tables, and examples

Constraints — Different types (e.g., UNIQUE, NOT NULL, CHECK, DEFAULT), syntax, and practical examples

Suggested Change

I would like to add above mention documentations .

Rationale

No response

Urgency

Medium

Record

• I have read the Contributing Guidelines
• Are you a GSSOC'25 contributor
• I want to work on this issue

[github-actions]

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[github-actions]

👤 Issue assigned to @dinesh-2047.

[github-actions]

✅ This issue has been closed. Thank you for your contribution!