Select controls the structure of the stream. You can keep or remove fields, rename them, change a type and arrange the output columns. Use Metadata after the tool to confirm the result. A text identifier such as 0012 should usually remain text; converting it to an integer removes the leading zeros and changes its meaning as an identifier.
Numeric-looking source text needs a deliberate conversion rule. Invalid text cannot become a meaningful quantity just because you request a numeric type. Review conversion warnings and the resulting nulls. Field size matters for text as well: an undersized output can truncate values. Choose a size from the data contract rather than the first visible row. These tasks check the values and the resulting schema together.