MSSQL
Microsoft SQL Server is a proprietary relational database management system developed by Microsoft.
The SQL Server Wrapper allows you to read data from Microsoft SQL Server within your Postgres database.
Restoring a logical backup of a database with a materialized view using a foreign table can fail. For this reason, either do not use foreign tables in materialized views or use them in databases with physical backups enabled.
Supported Data Types
| Postgres Type | SQL Server Type |
|---|---|
| boolean | bit |
| char | tinyint |
| smallint | smallint |
| real | float(24) |
| integer | int |
| double precision | float(53) |
| bigint | bigint |
| numeric | numeric/decimal |
| text | varchar/char/text |
| date | date |
| timestamp | datetime/datetime2/smalldatetime |
| timestamptz | datetime/datetime2/smalldatetime |
Preparation
Before you get started, make sure the wrappers extension is installed on your database:
_10create extension if not exists wrappers with schema extensions;
and then create the foreign data wrapper:
_10create foreign data wrapper mssql_wrapper_10 handler mssql_fdw_handler_10 validator mssql_fdw_validator;
Secure your credentials (optional)
By default, Postgres stores FDW credentials inside pg_catalog.pg_foreign_server in plain text. Anyone with access to this table will be able to view these credentials. Wrappers is designed to work with Vault, which provides an additional level of security for storing credentials. We recommend using Vault to store your credentials.
_10-- Save your SQL Server connection string in Vault and retrieve the `key_id`_10insert into vault.secrets (name, secret)_10values (_10 'mssql',_10 'Server=localhost,1433;User=sa;Password=my_password;Database=master;IntegratedSecurity=false;TrustServerCertificate=true;encrypt=DANGER_PLAINTEXT;ApplicationName=wrappers'_10)_10returning key_id;
Connecting to SQL Server
We need to provide Postgres with the credentials to connect to SQL Server. We can do this using the create server command:
_10create server mssql_server_10 foreign data wrapper mssql_wrapper_10 options (_10 conn_string_id '<key_ID>' -- The Key ID from above._10 );
The connection string is an ADO.NET connection string, which specifies connection parameters in semicolon-delimited string.
Supported parameters
All parameter keys are handled case-insensitive.
| Parameter | Allowed Values | Description |
|---|---|---|
| Server | <string> | The name or network address of the instance of SQL Server to which to connect. Format: host,port |
| User | <string> | The SQL Server login account. |
| Password | <string> | The password for the SQL Server account logging on. |
| Database | <string> | The name of the database. |
| IntegratedSecurity | false | Windows/Kerberos authentication and SQL authentication. |
| TrustServerCertificate | true, false | Specifies whether the driver trusts the server certificate when connecting using TLS. |
| Encrypt | true, false, DANGER_PLAINTEXT | Specifies whether the driver uses TLS to encrypt communication. |
| ApplicationName | <string> | Sets the application name for the connection. |
Creating Foreign Tables
The SQL Server Wrapper supports data reads from SQL Server.
| Integration | Select | Insert | Update | Delete | Truncate |
|---|---|---|---|---|---|
| SQL Server | ✅ | ❌ | ❌ | ❌ | ❌ |
For example:
_10create foreign table mssql_users (_10 id bigint,_10 name text,_10 dt timestamp_10)_10 server mssql_server_10 options (_10 table 'users'_10 );
Foreign table options
The full list of foreign table options are below:
-
table- Source table or view name in SQL Server, required.This can also be a subquery enclosed in parentheses, for example,
_10table '(select * from users where id = 42 or id = 43)'
Query Pushdown Support
This FDW supports where, order by and limit clause pushdown.
Examples
Some examples on how to use SQL Server foreign tables.
Let's prepare the source table in SQL Server first:
_11-- Run below SQLs on SQL Server to create source table_11create table users (_11 id bigint,_11 name varchar(30),_11 dt datetime2_11);_11_11-- Add some test data_11insert into users(id, name, dt) values (42, 'Foo', '2023-12-28');_11insert into users(id, name, dt) values (43, 'Bar', '2023-12-27');_11insert into users(id, name, dt) values (44, 'Baz', '2023-12-26');
Basic example
This example will create a foreign table inside your Postgres database and query its data:
_11create foreign table mssql_users (_11 id bigint,_11 name text,_11 dt timestamp_11)_11 server mssql_server_11 options (_11 table 'users'_11 );_11_11select * from mssql_users;
Remote subquery example
This example will create a foreign table based on a remote subquery and query its data:
_11create foreign table mssql_users_subquery (_11 id bigint,_11 name text,_11 dt timestamp_11)_11 server mssql_server_11 options (_11 table '(select * from users where id = 42 or id = 43)'_11 );_11_11select * from mssql_users_subquery;