# SQL Data Types: A Practical Guide to Understanding > Data types in SQL define the format of each column: INT, VARCHAR, DATE, FLOAT, and others. The right type affects performance and quality. Source: https://www.erathos.com/en/blog/data-types-in-sql Em português: https://www.erathos.com/blog/data-types-in-sql Published: 2025-08-14 Category: Data Engineering ![SQL table with columns of different data types highlighting INT, VARCHAR, DATE, and FLOAT](https://cms-media.erathos.com/Header Blog.png) ## Fundamentals of SQL Data Types SQL data types are the foundation of any strategy for storing reliable information. If you work with databases, make decisions, or manage integrations, you know that using the correct types makes all the difference. It sounds simple, but a small error can turn into a major issue in data analysis down the road. With that in mind, I have prepared this guide to clearly explain the most important points on how to choose and properly use these categories. And if you want to ensure quality without complexity, see how Erathos helps B2B companies do this in a simple, secure, and hassle-free way. Continue reading to make your operations much more reliable and agile, and rely on Erathos to support your choices! ## What are SQL data types? When we talk about SQL data types, we are talking about the heart of information storage. They tell the system the format of the information in each column of your table. When creating or adjusting a database, you must specify whether that field will contain text, numbers, dates, binary values, among others, each of these choices has a direct impact on how you query, filter, or even integrate data using platforms like Erathos. In other words, defining [data types](https://www.erathos.com/blog/tipos-de-dados) is almost like giving an identity to each piece of stored data, and this will heavily define what you can do with it later. ## Key SQL Data Types There are several types, but some appear so often that you can almost imagine their "personalities." Below, I list the most common categories: ### Numeric (INT, DECIMAL, FLOAT) - INT is used for integers, such as item quantities, age, or IDs without decimal places. - DECIMAL specifies numbers with fixed decimal places, ideal when you need precision, such as financial values or exact measurements. - FLOAT allows floating-point numbers, great for scientific values or approximate results, but be careful: it can lose precision in some situations. Choosing between them will depend on how much detail you need. For age, INT works. But for unit cost, DECIMAL wins the game. ### Text (VARCHAR, CHAR, TEXT) - VARCHAR is used for variable-length text. Good for names, emails, descriptions, anything that can range from three to three hundred characters. - CHAR stores fixed-length text, so every entry in that field will always occupy the same space. It works well for abbreviations, standardized codes, or state initials. - TEXT comes into play for large bodies of text, such as extensive comments, logs, or documents. A personal tip: I've seen many people use VARCHAR for everything, thinking it's practical, but it's like putting everyone in the same uniform, even when it's not necessary. ### Date and Time (DATE, DATETIME, TIMESTAMP) - DATE stores only the date (year, month, day). - DATETIME brings date and time combined, storing down to seconds and milliseconds if needed. - TIMESTAMP is designed to record the exact moment of an action, almost always stored in UTC. Perfect for tracking when a row was created, for example. Dealing with sales history, lead sign-ups, or data update timestamps? These fields will be your best allies. ### Boolean, Binary, and Other Specific Types - BOOLEAN usually saves true or false. Ideal for fields like "active", "accepted terms", "sent". - BINARY/VARBINARY stores files, images, encrypted passwords, and non-textual content. - Other types: in more robust databases, you will also see UUID, ENUM, and geometric types, each for very specific scenarios. These types are not used all the time, but when they appear, they solve very practical issues, for example, ENUM to limit status options, or UUID for unique identifiers. ## When to Use Each Data Type The choice is not always obvious. Sometimes, doubts arise: should I use INT or DECIMAL? VARCHAR or TEXT? There is no universal answer, but understanding the rules below helps a lot. ### Precision Rules If information needs to be recorded with exact precision, think twice before using FLOAT. Monetary values, for example, require DECIMAL. However, calculation results that only need an approximate range can usually rely on FLOAT. For text, use CHAR only when you know the length will never vary. In other cases, prefer VARCHAR, as it offers flexibility and saves space. ### Impact on Performance and Storage I have seen databases struggle because everything was saved as text. It did not seem to make a difference at first, but later it led to slowness and inaccurate searches. Using INT for keys, BOOLEAN for flags, and proper types for dates keeps everything lightweight and fast. It also helps when joining data across systems using tools like Erathos, as the chance of errors decreases significantly. > Using the right types makes everything run smoother; you only realize one was missing after things get complicated. ## Best Practices When Defining SQL Data Types To ensure organized databases and avoid headaches, a few practices work in almost every scenario: ### Consistency, Integrity, and Conversions - Standardize the data type of an attribute across all related tables. For example, if an ID is INT in one table, it should be INT in the others. - Avoid mixing types for the same field, as automatic conversion can truncate data, round without warning, or yield unexpected query results. - Always define clear limits: text lengths, number of decimal places, minimum and maximum values, whenever possible. In data integration, as with the Erathos solution, this clarity becomes a golden rule. Even without altering the data's meaning, keeping a standard ensures everything arrives correctly from start to finish. ### Avoiding Excessive Use of Generic Types - Avoid saving everything as text or STRING. It is practical in the beginning, but becomes a headache when querying. - Choosing specific types helps protect data, increases query speed, and simplifies integration with BI tools or dashboards. Here, I see many companies taking the shortcut of saving everything as VARCHAR, "just in case." When it's time to build detailed reports or transform data, the effort required is always much greater. A conscious choice reduces rework. ## How Erathos Helps with the Right Choice of Types Erathos offers an integration platform focused on moving data between systems without losing quality. Even when data is delivered to the destination as text, the platform monitors and helps validate that the original schemas are correct at the source. This means that if you structure your source tables well, the Erathos bridge guarantees this precision all the way to the warehouse, making life easier for those doing downstream analysis. Unlike competitors, Erathos is simple to operate, without requiring a specialized technical team to check every single type. Everything is automated, with alerts for any non-compliance. And anyone who has used market alternatives knows: support is usually slow, metrics are lacking, and the setup scares off less experienced users. With Erathos, the experience is accessible and straightforward. > Trust your source structure and leave the secure movement to Erathos. ## FAQ ### What are the main SQL data types? The most common types in SQL include integers (INT), decimals (DECIMAL, NUMERIC), characters (VARCHAR, CHAR), date and time (DATE, DATETIME, TIMESTAMP), booleans (BOOLEAN), and binaries (BINARY, VARBINARY). Other types like ENUM, UUID, or geometric types exist in specific contexts. ### What is each data type used for? Each type defines how information is stored and processed. INT for integers, DECIMAL for values with decimal places, VARCHAR/CHAR for text, DATE/DATETIME/TIMESTAMP for dates and times, BOOLEAN for true/false, and BINARY for files and non-textual content. Using the correct type helps with queries, integrations, and avoids data loss or errors. ### How do I choose the ideal data type? Always consider what the field will be used for, the typical size of the information, the need for precision, desired performance, and compatibility with integration tools like Erathos. If you need to store financial values, choose DECIMAL. For short, variable-length text, use VARCHAR. Analyze the context of the information and never use generic types unnecessarily. ### Can I change the data type later? You can, but depending on the volume of data, the schema structure, and relationships with other tables, the change can be complex. Alterations require caution to avoid losing data, causing truncation, or breaking integrations. Whenever possible, plan well from the beginning. When you do need to make a change, always take a backup first! ### Which data type should I use for dates? It is recommended to use DATE if you only need the day, month, and year. For events that involve times, choose DATETIME or TIMESTAMP (the latter is great for logs or automatic update records). This keeps dates organized and easy to query or sort. ## Conclusion Getting your SQL data types right reduces errors, accelerates queries, and makes your pipelines ready for scaling and integrating with other solutions. With simple best practices, you can transform tables into reliable sources for analysis, BI, and valuable reporting. And, of course, using a platform designed for real-world scenarios makes all the difference: Erathos is your best partner on this journey. Want to ensure precision without complication? Talk to [Erathos ](https://www.erathos.com)and our specialists and see how to integrate, move, and prepare data for analysis painlessly, using the leading platform in B2B integration! !