1. A method for accessing a database and combining a plurality of transactions by a computer, the method comprising: receiving a plurality of transactions from a plurality of clients, wherein each of said plurality of transactions comprises a select query; combining said select queries in said transactions using a set operator, wherein said select query comprises a plurality of SQL statements; associating each of said SQL statements from said select queries to be combined with a client ID of said corresponding client; generating a first list of data types for each selected SQL statement, wherein said first list of data types comprises data types from said selected SQL statement and said corresponding client ID; generating a second list of data types, wherein said second list of data types comprises all said data types from said selected SQL statements; converting said SQL statements of each said client so that said data types of each said SQL statement are arranged in order of said data types of a corresponding data type set; storing a correspondence between said data types of a converted SQL statement and said data types of an unconverted SQL statement for each of said client IDs of said clients; combining all said converted SQL statements using said set operator; sending combined SQL statements to said database; and sending combined select queries to said database as a combined transaction.