1. A computer-implemented method of cleansing anomalies from sequence-based data at query time, comprising: loading sequence-based data into a database managed by a database management system (DBMS) of a computing system, said loading being performed at a load time of said sequence-based data that precedes a query time of said sequence-based data; receiving a cleansing rule at a cleansing rules engine of said computing system; automatically converting, by said cleansing rules engine, said cleansing rule to a template, said template including logic to compensate for one or more anomalies in said sequence-based data; receiving, at said query time and by a query rewrite engine of said computing system, a user query to retrieve said sequence-based data; automatically rewriting, at said query time and by said query rewrite engine, said user query to provide a rewritten query, said automatically rewriting including applying said logic included in said template to compensate for said one or more anomalies; and executing, at said query time, said rewritten query by said DBMS, wherein an answer provided by said executing said rewritten query is identical to a result of executing said user query on a set of data generated by an application of said cleansing rule to all of said sequence-based data.