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home / developersection / interviews / difference between identity vs sequence.
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Anubhav Sharma
Anubhav Sharma

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The Anubhav portal was launched in March 2015 at the behest of the Hon'ble Prime Minister for retiring government officials to leave a record of their experiences while in Govt service .

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1 Answers

Anubhav Sharma
Anubhav Sharma 07 May 2026
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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:

CREATE TABLE Employees (
    EmployeeID INT IDENTITY(1,1),
    Name VARCHAR(100)
);

Here:

  • First 1 = start value
  • Second 1 = increment

Inserted rows automatically get:

1, 2, 3, 4...

Characteristics

  • Bound directly to one table column
  • Mostly used for primary keys
  • Simpler setup
  • Less flexible

Common Databases Supporting IDENTITY

  • Microsoft SQL Server
  • PostgreSQL (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:

CREATE SEQUENCE emp_seq
START WITH 1
INCREMENT BY 1;

Use it:

INSERT INTO Employees(EmployeeID, Name)
VALUES(nextval('emp_seq'), 'John');

When to Use Which?

Use IDENTITY when:

  • Simple primary key generation
  • One table only
  • Minimal configuration needed
  • Standard CRUD applications

Use SEQUENCE when:

  • Multiple tables share numbering
  • Need custom numbering logic
  • Need numbers before insert
  • High scalability/concurrency
  • Enterprise 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.

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