Essential Types of Data in SQL: What Businesses Need to Know

Behind every successful custom software project is a reliable database.

At ioSTUDIOS, choosing the right SQL data type is one of the most important decisions you can make. It is not only a coding choice. It is a strategic choice that protects data quality, reduces storage, and keeps systems fast as they grow.

For businesses commissioning custom software, understanding the basics of SQL data types helps you build on a solid foundation.

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Why data types matter

Every column in a database table stores a specific kind of information, from customer names to transaction amounts. Picking the right data type helps you:

• Store numbers, text, and dates accurately
• Run reports and queries faster
• Avoid common errors such as unexpected nulls, truncated text, or silent type conversions

The wrong choice can cause problems. For example, using floating point numbers for money can lead to rounding errors in financial reports. Choosing a very large text size when a small one would do wastes space and slows queries. Our goal at ioSTUDIOS is to prevent those risks before they reach your business.

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Core SQL data type categories

While SQL engines offer many options, most projects rely on the types below.

1) Numeric data types

Use numeric types for counts, prices, and measurements.

• Exact numeric types:INT, BIGINT, and DECIMAL (also called NUMERIC).
  • Use INT or BIGINT for whole numbers, such as stock counts or IDs.
  • Use DECIMAL(p, s) for money and other values that must be exact. Example: DECIMAL(10,2) stores amounts like 12345.67.
• Approximate numeric types:FLOAT and REAL.
  • Good for scientific or statistical data where tiny differences are acceptable.
  • Not recommended for prices or invoices.

Rule of thumb: use exact numeric types for any business‑critical calculations.

2) String data types

Text appears everywhere, from names to product descriptions.

• CHAR(n): fixed length. Best for short, predictable values like country codes or fixed part numbers.
• VARCHAR(n): variable length. Best for names, emails, and notes.
• Unicode types (NCHAR, NVARCHAR): needed for multilingual text.

Pick the smallest length that comfortably fits your data. This saves space and improves performance.

3) Date and time data types

Dates and times are essential for scheduling, auditing, and analytics.

• DATE and TIME store separate parts of a timestamp.
• DATETIME and TIMESTAMP store both date and time together.
• DATETIMEOFFSET adds the time zone offset, which helps with global systems and daylight saving changes.

Best practice: store timestamps in UTC, then convert to local time for display. This keeps results consistent across regions and when working with values like the Unix epoch.

4) Binary data types

Use binary types for files and raw bytes.

• BINARY(n) and VARBINARY(n) store fixed or variable length binary data.
• Large items such as images or PDFs can be stored as BLOBs. For performance, it is often better to store large files outside the database and keep only a link in the table.

This approach scales well and keeps the database lean.

5) Specialized data types

Modern SQL engines include types that solve specific problems.

• Boolean: often BIT in Microsoft SQL Server, for true or false values
• Spatial: types like GEOGRAPHY for maps and logistics
• Semi‑structured: JSON and XML for flexible, structured text

Use these when they simplify your design or improve performance.

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Best practices for bespoke development

• Performance and storage: choose the smallest suitable type. This applies to both numbers and strings.
• Data integrity: use constraints to enforce valid values, set sensible defaults, and prevent invalid negatives. Where supported, the UNSIGNED attribute can help.
• Cross‑platform compatibility: engines differ. For example, Microsoft SQL Server supports MONEY, while MySQL historically allowed display width on integers. We handle these differences so your system behaves consistently.

Attention to these details helps your system grow without hitting limits later.

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Common pitfalls to avoid

• Using FLOAT for money instead of DECIMAL
• Allowing null values where they are not expected
• Forgetting to declare and validate variables in stored procedures
• Oversizing text columns or storing large files directly in tables

We design around these issues from day one.

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Frequently asked questions

What is the best way to store money in SQL?
Use DECIMAL or NUMERIC with a defined precision and scale, such as DECIMAL(19,4). This prevents rounding errors that can occur with floating point types.

How do I keep date and time accurate across regions?
Use DATETIMEOFFSET when you need to store the time zone offset. Also store timestamps in UTC and convert to local time in your application.

Should I store files in the database?
Keep small binary items in VARBINARY if needed. For large files, use external storage and save only a reference in the database. This improves performance and simplifies backups.

How do I maintain long‑term data integrity?
Apply constraints, set default values, and prevent invalid negatives. Use UNSIGNED where your engine supports it, or add check constraints.

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At ioSTUDIOS, we build bespoke software that lasts. By choosing the right SQL data types early in the design, you avoid costly errors and keep your system fast and scalable.

If you are planning a new project and want a platform that balances precision, performance, and flexibility, speak to us today. We would love to help.