Query builder in advanced searching mode in the search GenBank service. Users can build complex queries using the query builder. Query builder allows composing a query by adding simple filtering phrases or terms that are joined by logical operators. Users are able to choose the logical operator and a database field that will be searched to find the given phrase or term (point 2). They can also set additional limits on the records that should be returned in the result set (point 3). In the presented example, a user wants to find all nucleotide sequences in the Nucleotide database that correspond to HNF1A gene in human organism and are involved in the maturity onset diabetes of the young (MODY). He/she intends to search the term hnf1a in the Gene Name field (GENE), term human in the Organism field (ORGN), and term MODY in All fields (ALL). All filtering conditions are joined by the AND operator. Composed query, i.e. “hnf1a”[GENE] AND “human”[ORGN] AND “MODY”[ALL], is visible in the query/search box next to the database drop-down list at the top of the page. Additional constraints are set on the Publication Date in point 3.