In this guide, we will walk you through the process of troubleshooting and fixing the Error converting data type NVARCHAR to Numeric issue. This error usually occurs when you attempt to convert an NVARCHAR column to a numeric data type in SQL Server. The error occurs when the NVARCHAR column contains a value that cannot be converted to a numeric data type.
Table of Contents
Understanding the Error
The Error converting data type NVARCHAR to Numeric issue occurs when SQL Server tries to convert a non-numeric value in an NVARCHAR column to a numeric data type. For instance, when you attempt to update or insert data into a table that contains an NVARCHAR column with a non-numeric value, and a constraint or trigger exists that requires the column to have a numeric value, the error occurs.
SQL Server supports various data types for storing different types of data. NVARCHAR is a variable-length Unicode character data type, while numeric is a data type that can store exact numeric values with a fixed number of decimal places.
Common Causes
- Non-numeric characters in the NVARCHAR column
- Incorrect data type conversion function
- Implicit data type conversion
Step-by-Step Solution
Step 1: Identify the Non-Numeric Values
The first step in fixing the error is identifying the non-numeric values in the NVARCHAR column. You can use the ISNUMERIC function to filter out non-numeric values in the column. Here's an example query to find non-numeric values in the YourColumnName column of the YourTableName table:
SELECT *
FROM YourTableName
WHERE ISNUMERIC(YourColumnName) = 0
Step 2: Update or Remove Non-Numeric Values
Once you have identified the non-numeric values, you can either update them with numeric values or remove them altogether. To update a specific row, you can use the following query:
UPDATE YourTableName
SET YourColumnName = 'YourNewNumericValue'
WHERE YourPrimaryKeyColumn = 'PrimaryKeyValue'
To remove a specific row, you can use the following query:
DELETE FROM YourTableName
WHERE YourPrimaryKeyColumn = 'PrimaryKeyValue'
Step 3: Use the Correct Data Type Conversion Function
When converting an NVARCHAR column to a numeric data type, make sure you are using the correct data type conversion function. For instance, use the CAST or CONVERT function to explicitly convert the column to a numeric data type:
SELECT CAST(YourColumnName AS NUMERIC(18, 2))
FROM YourTableName
Or
SELECT CONVERT(NUMERIC(18, 2), YourColumnName)
FROM YourTableName
FAQ
What is the difference between NVARCHAR and VARCHAR data types?
- NVARCHAR is a Unicode variable-length character data type that can store both Unicode and non-Unicode characters.
- VARCHAR is a non-Unicode variable-length character data type that can store only non-Unicode characters.
How can I avoid implicit data type conversion?
To avoid implicit data type conversion, always use the correct data type for your columns when creating or altering tables. Also, use the CAST or CONVERT functions when you need to explicitly convert one data type to another.
What is the difference between CAST and CONVERT functions?
Both CAST and CONVERT functions are used to convert one data type to another. The main difference between the two is the syntax. The CAST function uses the ANSI SQL-92 syntax, while the CONVERT function uses the SQL Server-specific syntax.
Can I convert an NVARCHAR column to an INT data type?
Yes, you can convert an NVARCHAR column to an INT data type using the CAST or CONVERT functions. However, before converting, make sure that the NVARCHAR column contains only integer values, otherwise, an error will occur.
Can I use the TRY_CONVERT function to avoid the error?
Yes, you can use the TRY_CONVERT function to avoid the error. The TRY_CONVERT function returns a NULL value if the conversion fails, instead of raising an error. Here's an example:
SELECT TRY_CONVERT(NUMERIC(18, 2), YourColumnName)
FROM YourTableName