NULL_IF identifies one or more source-file strings that Snowflake should interpret as SQL NULL while loading data. For example, a file format can define NULL_IF = ( ' NULL ' , ' NUL ' , ' \N ' , ' ' ).
When Snowflake encounters any specified value in the CSV input, it loads a SQL NULL into the corresponding target column. The parameter does not remove rows or values from the dataset, convert binary content, or automatically replace NULL values with empty strings. Snowflake applies the conversion to every occurrence of a configured value, regardless of whether that value visually resembles text or a number. When unloading data, NULL_IF works in the opposite direction by converting SQL NULL values into the first specified output string, but this question specifically concerns loading CSV data.