A computer implemented method for integrating data into a target database may include: providing a plurality of source databases which each may include a relational schema and data for integration into the target database; generating at least one complexity model based on the relational schema and data of each source database, each complexity model indicating at least one inconsistency between two or more of the data sources which may be require to be resolved to integrate the data from the data sources into the target database; and generating an effort model that may include an effort value for each inconsistency indicated by each complexity model, each effort value indicating at least one of a time period and a financial cost to resolve the inconsistency to integrate data from the data sources into the target database.