Key Constraints in SQL | Dataford Interview Questions

Difference between Primary Key and Unique Key.

Asked in the Pre-Placement Interview stage. Using the PostgreSQL table provided, write a query that displays the table's primary key and unique constraints so their definitions can be compared directly.

Output

One row per primary key or unique constraint on candidate_accounts
Columns: constraint_name, constraint_type, and constraint_definition
Sort primary key constraints before unique constraints, then sort by constraint name

Schema

candidate_accounts

Column	Type	Description
account_idPK	INT	Primary identifier for the account
email	VARCHAR(255)	Email protected by a unique constraint
display_name	VARCHAR(100)	Displayed account name
account_status	VARCHAR(20)	Current account status

Your question is Key Constraints in SQL. Start with the requirements and the one table in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Difference between Primary Key and Unique Key.

Output

One row per primary key or unique constraint on candidate_accounts
Columns: constraint_name, constraint_type, and constraint_definition
Sort primary key constraints before unique constraints, then sort by constraint name

Schema

candidate_accounts

Column	Type	Description
account_idPK	INT	Primary identifier for the account
email	VARCHAR(255)	Email protected by a unique constraint
display_name	VARCHAR(100)	Displayed account name
account_status	VARCHAR(20)	Current account status

Your question is Key Constraints in SQL. Start with the requirements and the one table in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.