Returns a rowset from a data extension where the field matches the specified value. The system treats strings as case-sensitive. Specify additional field value pairs as part of an AND clause. This function returns a maximum of 2000 rows. To better control the number or the order of returned rows, use the LookupOrderedRowsCS() function. This limitation enhances script performance.

LookupRowsCS(1, 2, 3)

1stringRequiredName of data extension from which to return specified rows
2stringRequiredColumn name used to identify rows to return
3stringRequiredValue used to match rows to return