By default, searches performed from the MIDM follow the logic defined in the configured basic queries. You can specify which query type to use for each search defined for the MIDM (this is specified in midm.xml). These searches can be weighted, which means that the match engine calculates the likelihood that the search results match the actual search criteria and assigns a matching weight to each returned record. You can specify whether the search is performed on the original or phonetic version of the criteria.
The basic query uses all supplied search criteria to create a single SQL query. For this query, each field in the WHERE clause is joined by an AND operator, meaning that only records that match on all search fields are returned. This query has an option to allow wildcard characters in the search criteria (a percent sign (%) indicates multiple unknown characters). When this option is set to true, the query uses the LIKE operator rather than EQUALS. This option allows you to search by criteria for which you have incomplete data.
The searches performed from the MIDM can be further customized in midm.xml (for more information, see Master Index Data Manager Configuration).