SSIS: Cannot map the lookup column because the column is set to a floating point data type

Question

Even though I have defined float type, I still can't map. I got this error:

Cannot map the lookup column, 'vertical_rate', because the column is set to a floating point data type.

Bummer

What are the types of the columns in the source and the destination ? – Carney

float will never match. A value of 1 is often rendered as 1.000000000001 or .99999999997. If you have to use float and you are trying to use these columns to join, you may want to round and change your data type. – Florey

Answer 1

According to the Microsoft documentation on the Lookup transformation (https://learn.microsoft.com/en-us/sql/integration-services/data-flow/transformations/lookup-transformation?view=sql-server-ver16), you cannot use the floating-point data type (DT_R8, which is a double-precision floating-point value) to do a Lookup:

The transformation supports join columns with any data type, except for DT_R4, DT_R8, DT_TEXT, DT_NTEXT, or DT_IMAGE. For more information, see Integration Services Data Types.

This is because, as @KeithL correctly points out, floating point is not exact. If the reference dataset uses floating point, then you must first change the data type there first. Then use a compatible data type for the matching input field used to join.

Georgiageorgian