SQL Server Integration Services (SSIS) is a powerful tool used for data integration and transformation. However, one common issue that developers face while working with SSIS is the error message “Cannot convert between Unicode and non-Unicode string data types”. This error occurs when there is a mismatch in data types between the columns in the source and destination tables.
Understanding Unicode and Non-Unicode Data Types
Unicode is a character encoding standard that includes characters from all the major languages and scripts in the world. It uses 16 bits to represent each character, which allows it to support a larger range of characters than non-Unicode encoding standards.
Non-Unicode, also known as ANSI, is a character encoding standard that uses a single byte to represent each character. It was originally designed for the English language, but has since been extended to support other languages as well. However, it does not support as many characters as Unicode.
Causes of the “Cannot convert between Unicode and non-Unicode string data types” Error
The “Cannot convert between Unicode and non-Unicode string data types” error occurs when there is a mismatch in data types between the source and destination tables in an SSIS package. This can happen due to several reasons:
- The source and destination tables have different data types for the same column
- The source table has a non-Unicode data type and the destination table has a Unicode data type
- The source table has a Unicode data type and the destination table has a non-Unicode data type
Resolving the “Cannot convert between Unicode and non-Unicode string data types” Error
There are several ways to resolve the “Cannot convert between Unicode and non-Unicode string data types” error in SSIS:
- Ensure that the data types of the source and destination tables match for each column
- Convert the data types of the columns in the source or destination tables to match each other
- Use a data conversion task in the SSIS package to convert the data types of the columns
It is important to note that simply changing the data types of the columns in the source or destination tables may not always be feasible, especially if the tables are used by other applications or systems as well. In such cases, using a data conversion task is a better solution.
Using a Data Conversion Task in SSIS
A data conversion task in SSIS is used to convert the data types of columns from one type to another. It can be used to convert non-Unicode data types to Unicode and vice versa, as well as to convert between other data types.
To use a data conversion task in SSIS, follow these steps:
- Add a data conversion task to the SSIS package
- Configure the data conversion task to convert the columns with the mismatched data types
- Map the output of the data conversion task to the destination table
It is important to ensure that the data types of the columns in the source table match the input data types of the data conversion task, and that the output data types of the data conversion task match the data types of the columns in the destination table.
Conclusion
The “Cannot convert between Unicode and non-Unicode string data types” error is a common issue faced by developers while working with SSIS. It occurs due to a mismatch in data types between the source and destination tables. To resolve this error, it is important to ensure that the data types of the columns in the source and destination tables match, or to use a data conversion task in the SSIS package to convert the data types of the columns.