Difference between IDENTITY vs SEQUENCE.

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Anubhav Sharma · Answer

IDENTITY and SEQUENCE are both used to generate numeric values automatically in SQL databases, but they work differently and are suited for different scenarios. Quick Comparison Feature IDENTITY SEQUENCE Tied to a table column Yes No Reusable across tables No Yes Generates values automatically on insert Yes Usually via NEXT VALUE FOR / nextval() Custom control over generation Limited More flexible Can generate numbers before insert No Yes Reset/restart support Limited Easier Standard SQL feature Vendor-specific origins ANSI SQL standard 1. IDENTITY An IDENTITY column auto-generates values when rows are inserted. Example in Microsoft SQL Server: Here: First 1 = start valueSecond 1 = increment Inserted rows automatically get: Characteristics Bound directly to one table columnMostly used for primary keysSimpler setupLess flexible Common Databases Supporting IDENTITY Microsoft SQL ServerPostgreSQL (GENERATED AS IDENTITY)Oracle Database (12c+)IBM Db2 2. SEQUENCE A SEQUENCE is an independent database object that generates numbers. Example in Oracle Database or PostgreSQL: Use it: When to Use Which? Use IDENTITY when: Simple primary key generationOne table onlyMinimal configuration neededStandard CRUD applications Use SEQUENCE when: Multiple tables share numberingNeed custom numbering logicNeed numbers before insertHigh scalability/concurrencyEnterprise workflows Interview-Friendly Summary IDENTITY is a table-bound auto-increment column, while SEQUENCE is an independent object that generates reusable numeric values with greater flexibility and control.

Feature	IDENTITY	SEQUENCE
Tied to a table column	Yes	No
Reusable across tables	No	Yes
Generates values automatically on insert	Yes	Usually via `NEXT VALUE FOR` / `nextval()`
Custom control over generation	Limited	More flexible
Can generate numbers before insert	No	Yes
Reset/restart support	Limited	Easier
Standard SQL feature	Vendor-specific origins	ANSI SQL standard

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Difference between IDENTITY vs SEQUENCE.

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Quick Comparison

1. IDENTITY

Characteristics

Common Databases Supporting IDENTITY

2. SEQUENCE

When to Use Which?

Use IDENTITY when:

Use SEQUENCE when:

Interview-Friendly Summary