MS SQL Server and PostgreSQL Datatypes Comparison

If you are thinking of transferring data from MS SQL Server to PostgreSQL or vice versa, the following comparison should be useful. Both MS SQL Server and PostgreSQL support a wide array of datatypes, including standard ones like integers, strings, and dates — but the names and behavior of these datatypes may differ between the two.

Numeric Datatypes

Datatype	MS SQL Server	PostgreSQL	Notes
Integer	`INT`	`INTEGER`	Both platforms support signed integers.
Big Integer	`BIGINT`	`BIGINT`	Used for larger integer values.
Small Integer	`SMALLINT`	`SMALLINT`	A smaller range of integer values.
Decimal	`DECIMAL(p, s)`	`DECIMAL(p, s)`	Precision-based decimal numbers.
Floating Point	`FLOAT(n)`	`FLOAT(n)`	Floating-point numbers with precision.
Real Numbers	`REAL`	`REAL`	Less precise floating-point type.

String and Text Datatypes

Datatype	MS SQL Server	PostgreSQL	Notes
Fixed-length string	CHAR(n)	CHAR(n)	Both platforms support fixed-length.
Variable-length string	VARCHAR(n)	VARCHAR(n)	Variable-length strings.
Text	TEXT	TEXT	Large blocks of text data.
Unicode	NVARCHAR(n)	VARCHAR(n)	PostgreSQL handles Unicode in VARCHAR.

Datatype	MS SQL Server	PostgreSQL	Notes
Date	DATE	DATE	Basic date storage.
Time	TIME	TIME	For storing time-of-day values.
Timestamp	DATETIME, DATETIME2	TIMESTAMP	MS SQL Server has multiple timestamp types.
Time with time zone	DATETIMEOFFSET	TIMESTAMPTZ	Stores time with time zone information.

Datatype	MS SQL Server	PostgreSQL	Notes
Boolean	BIT	BOOLEAN	BIT in SQL Server stores 1/0 values.
Binary Data	VARBINARY(n)	BYTEA	Storing binary data like images/files.

Datatype	MS SQL Server	PostgreSQL	Notes
XML	XML	XML	Both platforms support XML storage.
JSON	NVARCHAR, JSON	JSON, JSONB	PostgreSQL has native JSON support.
UUID	UNIQUEIDENTIFIER	UUID	PostgreSQL natively supports UUID.
Array	Not Supported	ARRAY	PostgreSQL supports arrays natively.

Differences in Datatypes

Boolean Type: PostgreSQL has a dedicated BOOLEAN type that stores true/false values. MS SQL Server uses BIT for this, where 1 represents true and 0 represents false.
Text Storage: While both systems support TEXT, PostgreSQL handles text fields more flexibly, allowing easier manipulation and storage of larger blocks of text without performance degradation. MS SQL Server has different limits based on the type of text data stored, such as VARCHAR(MAX) for variable-length text.
JSON Support: PostgreSQL offers two types for JSON data — JSON (unprocessed) and JSONB (binary, optimized for search and manipulation). MS SQL Server does support JSON, but stores it in NVARCHAR fields, which lacks some of PostgreSQL's optimizations.
Array Support: PostgreSQL supports array types (ARRAY), allowing more complex data structures in a single column. MS SQL Server has no built-in array support, though similar functionality can be achieved through table structures or XML/JSON storage.
UUID Support: PostgreSQL provides native support for the UUID type, while MS SQL Server requires UNIQUEIDENTIFIER, which lacks some of the flexibility offered by PostgreSQL's implementation.

Main Differences Between MS SQL Server and PostgreSQL

1. Licensing and Costs

MS SQL Server is a commercial product with licensing fees, though a free version (SQL Server Express) with certain limitations is available. PostgreSQL is open-source and completely free for both commercial and noncommercial use, making it more cost-effective for businesses looking to reduce software expenses.

2. Operating System Compatibility

MS SQL Server was traditionally Windows-only but now also runs under Linux, though most customers still prefer Windows environments. PostgreSQL is designed for cross-platform deployment — it runs on Windows, Linux, macOS, and other Unix-based systems.

3. Performance and Scalability

MS SQL Server boasts advanced features such as in-memory OLTP, columnstore indexes, and parallel query processing, making it suitable for enterprise-grade applications. PostgreSQL is widely renowned for its scalability, particularly when handling complex queries and JSON/array datatypes, and its Multi-Version Concurrency Control model enables high concurrency without locking rows.

4. Replication and High Availability

MS SQL Server offers Always On Availability Groups, Database Mirroring, and Log Shipping. PostgreSQL supports multiple replication methods, including streaming replication, logical replication, and hot standby.

5. Extensibility

PostgreSQL is highly extensible, letting users define custom datatypes, operators, and functions, with an expansive ecosystem of extensions such as PostGIS. MS SQL Server offers extensibility through CLR integration, allowing .NET languages like C# to write custom functions, though it's less flexible than PostgreSQL for creating custom datatypes.

6. Community and Support

Microsoft offers robust commercial support for SQL Server, though development remains tightly controlled. PostgreSQL has an active, diverse open-source community that continuously contributes to the core product, and several third-party companies offer commercial support.

Summary

MS SQL Server and PostgreSQL are both powerful RDBMS platforms that serve different users and workloads. MS SQL Server offers feature-rich commercial solutions tailored for enterprise environments, while PostgreSQL appeals to developers and businesses looking for open-source flexibility, cross-platform compatibility, and advanced features such as JSON and array support. Understanding these datatype and functional differences will help you select the ideal platform for your project's requirements.

You can download Data Loader to automatically migrate data from MSSQL to PostgreSQL, or from PostgreSQL to MSSQL.