Introduction
When importing a file into a list, the volume of excluded lines is available
on the summary page for a list being configured;
in the Activity tab details for a list already configured.
Explanations
Excluded lines correspond to duplicates or lines with incorrect format.
Dupicates
Among rows with the same primary key combination, only one is kept randomly.
See Understanding primary keys
Invalid format
Lines with empty or invalid content are excluded:
lines with at least one mandatory empty column;
lines with a number of columns not corresponding to the configured schema. If the truncate ragged lines parameter is enabled, lines with too many columns will be inserted truncated. But rows with fewer columns will be excluded.
rows with a field type not matching the configured one
The incorrect format of these lines may come from the file but also from an incorrect definition of the column delimiter or text qualifier.
Conclusion
When importing a file, only lines that respect the defined configuration are added to the list.