SQL Conversion Failed Error

The error “Conversion failed when converting date and/or time from character string” in Microsoft SQL Server can be frustrating to deal with, especially when working with dates and times that contain spaces. In this article, we’ll explore the cause of this error and how to resolve it.

Understanding Date and Time Data Types

Before diving into the solution, let’s take a closer look at the date and time data types in SQL Server.

SQL Server supports two main date and time data types: datetime and date.

• The datetime data type represents a value with both date and time components. It has a resolution of 100 nanoseconds.
• The date data type, on the other hand, only represents dates without times. It is useful for storing historical dates or events.

The Issue at Hand

The error “Conversion failed when converting date and/or time from character string” occurs when SQL Server attempts to convert a date and/or time value from a character string into one of its data types (i.e., datetime or date). This conversion failure typically happens when the input contains spaces, which are not allowed in these data types.

The Role of the Conversion Style

The problem lies in the way we specify the conversion style. SQL Server has a number of conversion styles that define how to interpret the input character string. These styles can be specified using various functions, including CONVERT, CAST, and others.

• The CONVERT function allows you to specify multiple conversion styles as separate arguments.
• The CAST function is similar but uses the ANSI standard for conversion styles.

Solution: Specifying the Conversion Style Correctly

To resolve the “Conversion failed” error, we need to ensure that we’re using the correct conversion style. In this case, the issue arose from specifying the style as 126, which expects no spaces in the date and time values.

Here’s how you can modify your SQL query to use the correct conversion style:

CONVERT(DATETIME, '2017-09-22 20:31:48.000', 120)

In this example, we’re using the CONVERT function with a conversion style of 120, which ignores spaces in date and time values.

Example Queries

Here are some examples to illustrate how you can use the correct conversion style:

-- Using CONVERT
INSERT INTO [mytable] ([Date1], [Date2], [Date3])
VALUES (CONVERT(DATETIME, '2017-09-22 20:31:48.000', 120),
        CONVERT(DATE, '2017-09-22', 126),
        CONVERT(DATETIME, '2017-09-23 04:07:46.000', 120))

-- Using CAST
INSERT INTO [mytable]([Date1], [Date2], [Date3])
VALUES 
     (CAST('2017-09-22 20:31:48.000' AS DATETIME),
      CAST('2017-09-22' AS DATE),
      CAST('2017-09-23 04:07:46.000' AS DATETIME))

Best Practices

To avoid the “Conversion failed” error in the future, keep the following best practices in mind:

• When working with dates and times, ensure that you’re using the correct conversion style.
• Use a consistent conversion style throughout your SQL queries.
• Consider using date and time data types that don’t have spaces (e.g., date) when storing historical dates or events.

Conclusion

The “Conversion failed” error in Microsoft SQL Server can be frustrating, but it’s often caused by incorrect use of the conversion style. By understanding how to specify the correct conversion style, you can avoid this error and ensure that your date and time values are converted correctly.

Last modified on 2023-11-26