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, wherein said automatically rewriting includes applying said logic included in said template to compensate for said one or more anomalies and wherein said automatically rewriting further includes performing at least one of: an expanded rewrite algorithm and a join-back algorithm to generate said rewritten query, said performing including: reducing said sequence-based data to a subset of said sequence-based data, said subset to be used by a generation of cleansed data; and executing, subsequent to said reducing, logic included in said user query on said cleansed data; 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, and wherein said reducing said sequence-based data to said subset and said executing said logic included in said user query provide an assurance that said answer provided by said executing said rewritten query is identical to said result of said executing said user query on said set of data generated by said application of said cleansing rule to all of said sequence-based data.