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SQL Server to PostgreSQL Converter - Free Migration Tool 2025 | AI2sql

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SQL Server to PostgreSQL Converter - Free Migration Tool 2025 | AI2sql

SQL Server to PostgreSQL Converter - Free Online Tool 2025

Migrating from SQL Server to PostgreSQL is a common challenge for enterprises pursuing open-source adoption, cloud modernization, or cost optimization. Despite both being powerful relational databases, converting SQL Server queries, schema, and data to work seamlessly on PostgreSQL is complex due to syntax differences, data type mismatches, and platform-specific functions. Manual rewrite is slow, error-prone, and risky for business-critical workloads.

AI2sql offers a smarter path. As an intelligent migration solution, it generates PostgreSQL-compliant SQL directly from natural language or existing SQL Server statements, eliminating tedious code reviews and translation errors. Whether you're modernizing legacy systems or scaling analytics in the cloud, AI2sql minimizes downtime and maximizes migration success for teams of any size.

SQL Server to PostgreSQL Migration Overview

Enterprises often migrate from SQL Server to PostgreSQL to leverage open-source flexibility, cloud compatibility, and lower licensing fees. Key migration steps include:

  • Schema conversion (tables, indexes, constraints)

  • Data type mapping

  • View, procedure, and function translation

  • Data transfer and integrity checks

  • Optimization and validation

Each stage presents unique conversion challenges, amplified in large or complex environments. AI2sql accelerates SQL code transformation for a robust, secure PostgreSQL migration.

Key Syntax Differences: SQL Server vs PostgreSQL

Operation

SQL Server Syntax

PostgreSQL Syntax

Select Top N Rows

SELECT TOP 5 * FROM Employees

SELECT * FROM Employees LIMIT 5

String Concatenation

SELECT FirstName + ' ' + LastName

SELECT FirstName || ' ' || LastName

Auto-increment

INT IDENTITY(1,1)

SERIAL

Get Current Date/Time

GETDATE()

CURRENT_TIMESTAMP

Explicit Join

SELECT * FROM A INNER JOIN B ON A.ID = B.ID

SELECT * FROM A INNER JOIN B ON A.ID = B.ID

IF Statement

IF (@value = 1) SELECT 'Yes'

DO $$ BEGIN IF value = 1 THEN RAISE NOTICE 'Yes'; END IF; END $$;

Data Type Mapping Guide

Data type compatibility is critical for accurate migrations. This guide summarizes common type conversions:

SQL Server

PostgreSQL

INT

INTEGER

VARCHAR(n)

VARCHAR(n)

NVARCHAR(n)

VARCHAR(n)

DATETIME

TIMESTAMP

BIT

BOOLEAN

MONEY

NUMERIC

UNIQUEIDENTIFIER

UUID

Common Conversion Challenges

  • String operations: SQL Server’s + for concatenation vs PostgreSQL’s ||

  • Auto-increment columns: IDENTITY is replaced by SERIAL or GENERATED BY DEFAULT AS IDENTITY

  • Function differences: e.g., GETDATE() becomes CURRENT_TIMESTAMP

  • Stored procedures: T-SQL syntax must be re-authored for PostgreSQL’s PL/pgSQL

  • Boolean logic: BIT vs BOOLEAN requires data normalization

Manual conversion risks conversion errors, data loss, or incompatible queries.

Step-by-Step Migration Process

  1. Assess and inventory: List all SQL Server objects to migrate.

  2. Schema conversion: Map tables, indexes, constraints using AI2sql for accurate PostgreSQL code generation.

  3. Data type mapping: Convert columns to PostgreSQL-native types.

  4. Query and procedure translation: Use AI2sql to refactor queries, joins, and functions.

  5. Data migration: ETL tools or scripts for reliable data replication.

  6. Testing: Validate queries, edge cases, and transaction accuracy.

  7. Optimization: Tune indexes and performance settings for PostgreSQL.

AI2sql: Generate PostgreSQL Queries from Natural Language

AI2sql streamlines SQL Server to PostgreSQL conversion by:

  • Accepting English-language instructions or legacy SQL Server code

  • Transforming logic and syntax for the PostgreSQL target environment

  • Supporting 15+ databases and all major SQL dialects

  • Delivering instant, error-free PostgreSQL statements

Skip manual conversion - Generate PostgreSQL queries instantly with AI2sql using natural language.

Performance Considerations

  • Index usage: Rebuild indexes for PostgreSQL to optimize query speed

  • Connection pooling: Leverage PostgreSQL’s robust pooling solutions for high concurrency

  • Vacuum and analyze: Use regularly to maintain data health and performance

Schema Migration Best Practices

  • Primary and foreign keys: Validate enforcement of referential integrity

  • Explicit constraints: Migrate CHECK, UNIQUE, and NOT NULL constraints accurately

  • Reserved keywords: Rename columns/tables to avoid collisions in PostgreSQL

Testing and Validation

  • Develop automated unit and regression tests for business logic

  • Validate row/column counts and data accuracy after migration

  • Use EXPLAIN ANALYZE to compare query plans and optimize as needed

Rollback Strategies

  • Take full logical backups pre-migration

  • Stage migrations in a test environment before production cutover

  • Create migration scripts with version control for repeatability

Troubleshooting Common Conversion Errors

  • Unrecognized data types: Map them manually or use AI2sql’s auto-mapping suggestions

  • Syntax errors: Review function names and string operations

  • Constraint failures: Ensure data matches new UNIQUE/NOT NULL requirements

PostgreSQL Performance Optimization Tips

  • Use appropriate INDEX types: B-tree, Hash, or GIN for specific workloads

  • Partition large tables for faster queries

  • Tune work_mem, maintenance_work_mem, and shared_buffers

5 Practical SQL Server to PostgreSQL Conversion Examples

Description

SQL Server

PostgreSQL

Top N Rows

Datetime Conversion

String Concatenation

Auto-Increment Key

Conditional Logic

Conversion Examples: Syntax at a Glance

Operation

SQL Server

PostgreSQL

Select with Alias

Left Join

Date Function

UUID Generation

For more, explore our PostgreSQL SQL Tutorial.

Why Use AI2sql for Enterprise-Grade SQL Migration?

  • Supports all major databases and SQL dialects

  • No syntax expertise required – just describe your logic

  • Error-free conversions save time and prevent costly mistakes

  • Used by 50,000+ developers and DBAs for secure, high-accuracy migrations

  • Scalable for small projects and global enterprises

See more SQL Server Migration Tools to complement your migration journey.

The AI2sql platform delivers production-grade migration capabilities, from simple query rewriting to complex stored procedure conversions and end-to-end database modernization.

Skip manual conversion - Generate PostgreSQL queries instantly with AI2sql using natural language.

Conclusion: Make Your SQL Server to PostgreSQL Migration Error-Free

Migrating from SQL Server to PostgreSQL unlocks modern data agility, but it’s fraught with complexity, syntax pitfalls, and risk of human error. AI2sql transforms this challenge into a seamless process: rapidly converting SQL Server queries and schema to PostgreSQL, adapting data types, and restructuring business logic with production-grade precision. For teams seeking simplicity without sacrificing accuracy, AI2sql is the migration tool of choice.

Try AI2sql Free - Generate PostgreSQL Queries from Plain English

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