SQL data types explained: MySQL, Postgres & SQL Server cheat sheet

Working with databases? Then you've probably bumped into SQL data types. They might seem straightforward, but choosing the right ones can make or break your database's performance. In this blog, we'll dive into the world of SQL data types and why they're so important.

We'll explore how different databases like MySQL, PostgreSQL, and SQL Server handle data types, and share some handy cheat sheets. Plus, we'll go over best practices to help you design efficient and robust databases. Let's get started!

Understanding SQL data types

Data types are basically how databases know what kind of data to expect in each column. They're super important because they keep your data consistent and help with storage and retrieval speeds. Generally, data types fall into a few main groups: numeric, character (or string), date/time, and some miscellaneous ones.

Numeric types, as you'd guess, are for numbers—integers and decimals. Think INT, DECIMAL, FLOAT, and so on. Then we've got character or string types for text data, like CHAR and VARCHAR.

Date and time types handle, well, dates and times. Examples are DATE, TIME, and DATETIME. And for the miscellaneous stuff, we have types like BOOLEAN for true/false values and BLOB for binary data.

Picking the right data type is crucial for keeping your data accurate and your database running smoothly. It helps avoid inconsistencies and makes storage more efficient. It's worth trying out different types to see how they affect your project.

Comparing data types across MySQL, PostgreSQL, and SQL Server

Now, let's talk about how different databases handle data types. Even though MySQL, PostgreSQL, and SQL Server share a lot of common ground, there are some key differences. They all support the basic numeric, character, and date/time types, but the names and details can vary. For instance, MySQL uses TINYINT, MEDIUMINT, and BIGINT, while PostgreSQL and SQL Server have SMALLINT and BIGINT.

Each database also has its own unique data types that can be pretty handy. PostgreSQL, for example, offers arrays, hstore for key-value pairs, and geometric types. SQL Server includes types like XML, CURSOR, and SQL_VARIANT. On the flip side, MySQL supports ENUM and SET. These specialized types are great for specific use cases and can boost functionality when used right.

But here's the catch: these differences in data types can make it tricky when you're working across multiple databases or planning a migration. You might need to tweak your schemas and data to make everything work smoothly. That's where database-agnostic design principles and evolutionary database design techniques come in—they can help you navigate these compatibility issues.

At the end of the day, picking the right data types for your needs is key to keeping your database running efficiently. It's a good idea to check out cheat sheets and comprehensive guides to get familiar with the ins and outs of each database's data types. By taking advantage of each platform's strengths and being aware of their differences, you can build databases that are both robust and efficient.

SQL data types cheat sheet for MySQL, PostgreSQL, and SQL Server

Here's a handy cheat sheet for SQL data types across MySQL, PostgreSQL, and SQL Server!

MySQL data types:

• INT: Stores whole numbers from -2,147,483,648 to 2,147,483,647.

• VARCHAR(n): Stores variable-length strings up to 65,535 characters.

• DATETIME: Stores dates and times in the format 'YYYY-MM-DD HH:MM:SS'.

Example:

PostgreSQL data types:

• INTEGER: Stores whole numbers from -2,147,483,648 to 2,147,483,647.

• TEXT: Stores variable-length strings with no maximum length.

• TIMESTAMP: Stores dates and times with timezone information.

Example:

SQL Server data types:

• BIGINT: Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.

• NVARCHAR(n): Stores variable-length Unicode strings up to 4,000 characters.

• DATE: Stores dates in the format 'YYYY-MM-DD'.

Example:

When choosing data types, keep these tips in mind:

• Use the smallest data type that can handle your data—you'll save on storage space.

• For strings, decide between fixed-length (CHAR) and variable-length (VARCHAR) based on how consistent your data sizes are.

• Pick the right date and time types (DATE, DATETIME, TIMESTAMP) for your temporal data.

At Statsig, we often see how important it is to choose the right data types when working with different databases. Understanding these differences can make a big difference in your project.

For more details, check out this SQL data types cheat sheet.

Best practices for choosing SQL data types in database design

Choosing the right SQL data types is super important for storage efficiency and query performance. Using the smallest data type that fits your data can save space and speed up queries. For instance, if your numbers can fit within the INT range, there's no need to use a BIGINT.

If you're migrating or replicating databases, keep an eye on data type differences between platforms. Use tools like Liquibase or Flyway to manage schema changes and keep your data intact during migrations. And don't forget to test your queries on the new platform to spot any compatibility issues.

To stay on top of SQL data types, make use of cheat sheets and documentation specific to your database system. Tools like TablePlus offer a modern GUI for working with various databases, making it easier to explore and manage data types. It's a good habit to regularly review your database schema and tweak data types as your data changes.

Also, consider using the right data types for special cases. Types like BOOLEAN for true/false values or ENUM for a fixed set of options can boost data integrity and make your queries simpler. Just be cautious with vendor-specific data types—they might cause headaches if you need to switch databases in the future.

Closing thoughts

Understanding SQL data types is key to building efficient, reliable databases. By choosing the right types and being aware of the differences across MySQL, PostgreSQL, and SQL Server, you can optimize performance and ensure data integrity. Don't hesitate to use resources like cheat sheets and comprehensive guides to help you along the way.

At Statsig, we've seen firsthand how crucial the right data types are in making data-driven decisions. If you're interested in learning more, check out the links provided throughout this blog. Hope you find this useful!