SQL Server data types

This lesson uses the unmodified DDI_SQL_Training dataset v1.0.0 on SQL Server 2019 or later. Read common integer, date, decimal, text, and bit values without confusing storage with display.

Run the example

SELECT TOP (3) EmployeeID, FirstName, HireDate, AnnualSalary
FROM dbo.Employees
ORDER BY EmployeeID;

Read it step by step

1. EmployeeID is an int key; FirstName is nvarchar(40) Unicode text.
2. HireDate is a date without a time of day; AnnualSalary is decimal(10,2) with two fractional digits.
3. TOP (3) and ORDER BY EmployeeID select a repeatable three-row sample.

Check the result

These are the first three employees by EmployeeID, not the first rows stored in a table.

Practice

The values ProductID, ListPrice, and IsActive display do not reveal their types. Use sys.columns to list the declared data type, precision, and scale of those three Products columns.

SELECT c.name AS ColumnName, TYPE_NAME(c.user_type_id) AS DataType,
       c.precision AS [Precision], c.scale AS Scale
FROM sys.columns AS c
WHERE c.object_id = OBJECT_ID(N'dbo.Products')
  AND c.name IN (N'ProductID', N'ListPrice', N'IsActive')
ORDER BY c.column_id;