How to load data from PostgreSQL to MS SQL Server

Access your data on PostgreSQL

The first step in migrating your PostgreSQL data to any kind of data warehouse solution is to access your data and start extracting it.

There are many ways of doing this like, for example, a logical replication log as previously mentioned. In this case, you need to listen to the log for changes on the database and you reflect them on the target system. When pulling data from a database you also need to be able to filter tables, columns, find a way to identify updates, and replicate the appropriate database schema considering also that it will end up in a columnar database for analytics.

Another way is by using a JDBC importer. In this case, any input configuration will contain all the appropriate values for the database authentication and connection. By appropriately configuring the JDBC importer you can control each table’s behavior during import and altering its schema as well if desired. Moreover, pagination of data importing can be simulated by querying tables in batching mode.

Transform and prepare your PostgreSQL data

After you have accessed your data on PostgreSQL, you will have to transform it based on two main factors,

  1. The limitations of the database that the data will be loaded onto
  2. The type of analysis that you plan to perform

Each system has specific limitations on the data types and data structures that it supports. Also, you have to choose the right data types. Again, depending on the system that you will send the data to you will have to make the right choices.

While for the most common data types the mapping choices may seem to be obvious, each database system will most probably support a set of more “sophisticated” and database-specific types whose mapping choices requires careful consideration since they can limit the expressivity of your queries and restrict your analysts on what they can do directly out of the database.

However, if you plan to push the data to another PostgreSQL database then you probably don’t have to worry about the data types, unless you have some reasons related to the analysis that you will perform.

Load your PostgreSQL data into Microsoft SQL Server

So, after you have managed to access your data on PostgreSQL and you have also figured out the structure that the data will have on your database, you need to load the data into the database, in our case into a Microsoft SQL Server.

As a feature-rich and mature product, MS SQL Server offers a large and diverse set of methods for loading data into a database. One way of importing data into your database is by using the SQL Server Import and Export Wizard. With it and through a visual interface you will be able to bulk load data from a number of data sources that are supported.

Another way for importing bulk data into an SQL Server, both on Azure and on-premises, is by using the bcp utility. This is a command-line tool that is built specifically for bulk loading and unloading of data from an MS SQL database.

Finally and for compatibility reasons, especially if you are managing databases from different vendors, you can BULK INSERT SQL statements.

In a similar way and as it happens with the rest of the databases, you can also use the standard INSERT statements, where you will be adding data row-by-row directly to a table. It is the most basic and straightforward way of adding data into a table but it doesn’t scale very well with larger datasets.

Updating your PostgreSQL data on MS SQL Server

As you will be generating more data on PostgreSQL, you will need to update your older data on an MS SQL Server database. This includes new records, together with updates to older records that for any reason have been updated on PostgreSQL.

You will need to periodically check PostgreSQL for new data and repeat the process that has been described previously while updating your currently available data if needed. Updating an already existing row on a SQL Server table is achieved by creating UPDATE statements.

Another issue that you need to take care of is the identification and removal of any duplicate records on your database. Either because PostgreSQL does not have a mechanism to identify new and updated records or because of errors on your data pipelines, duplicate records might be introduced to your database.

In general, ensuring the quality of the data that is inserted in your database is a big and difficult issue and MS SQL Server features like TRANSACTIONS can help tremendously, although they do not solve the problem in the general case.

The best way to load data from PostgreSQL to Microsoft SQL Server and possible alternatives

So far we just scraped the surface of what can be done with MS SQL Server and how to load data into it. The way to proceed relies heavily on the data you want to load, from which service they are coming from, and the requirements of your use case.

Things can get even more complicated if you want to integrate data coming from different sources. A possible alternative, instead of writing, hosting, and maintaining a flexible data infrastructure, is to use a product like RudderStack that can handle this kind of problem automatically for you.

RudderStack integrates with multiple sources or services like databases, CRM, email campaigns, analytics, and more. Quickly and safely move all your data from PostgreSQL to Microsoft SQL Server and start generating insights from your data.

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