1. A non-transitory computer-readable recording medium storing a program to cause a computer to execute a search method, the search method comprising: providing plural databases sharing management of plural attributes associated with an entity identifier capable of identifying an entity, each of the plural databases storing an entity identifier in association with an attribute value of one of the plural attributes and an attribute name; receiving a search request including plural search conditions, each of the plural search conditions containing a combination of an attribute name and an attribute value; separating the plural search conditions included in the search request into search conditions for individual databases in accordance with an attribute management table, the attribute management table having attribute records containing a database identifier capable of identifying one of the plural databases and an attribute name of an attribute managed in the one of the plural databases; storing, for each database, the search condition and the database identifier in a condition record stored in a condition storage; searching a search result management table by the database identifier and the search condition contained in each of the condition records, the search result management table having result records containing a database identifier of a search database, a first search condition, and a hit count representing an amount of entity identifiers found in a past search, the attribute value managed in association with the entity identifiers in the search database satisfying the first search condition; determining anterior search databases identified with the database identifiers contained in the result records, the result records containing a hit count which is less than or equal to a predetermined amount or a hit count within a predetermined lowest ranks; searching each of the anterior search databases by the search condition contained in the condition record containing the database identifier of the each of the anterior search databases to acquire a first search result including a first entity identifier, the attribute value managed in association with the first entity identifier in the each of the anterior search databases satisfying the search condition for the each of the anterior search databases; determining common entity identifiers included in common in the first search results and generating a new search condition by adding an entity identifier determined to be in common and searching each of posterior search databases to acquire a second search result including second entity identifiers, and where the posterior search database being out of the plural databases other than the anterior search databases, the attribute value managed in association with the second entity identifier in the each of the posterior search databases satisfies the search condition for the each of the posterior search database.