26. A programmed computer system for tuning a database query, comprising: a display for displaying at least one of a plurality of database queries of a database to a user; a user input allowing the user to select a database query from among the displayed database queries; and a processor for parsing the selected database query to determine that the database query includes a first operator and for automatically tuning the selected database query based on the structure of the database, the tuned database query being displayed to the user via the display, wherein automatically tuning the selected database query comprises: automatically selecting a first optimization mode if one or more statistics exist for a table identified by the database query, and selecting a second optimization mode is selected if one or more statistics do not exist for the table identified by the database query, and wherein automatically tuning the selected database query comprises automatically rewriting the selected database query by converting the first operator to a second operator.
26. A programmed computer system for tuning a database query, comprising: a display for displaying at least one of a plurality of database queries of a database to a user; a user input allowing the user to select a database query from among the displayed database queries; and a processor for parsing the selected database query to determine that the database query includes a first operator and for automatically tuning the selected database query based on the structure of the database, the tuned database query being displayed to the user via the display, wherein automatically tuning the selected database query comprises: automatically selecting a first optimization mode if one or more statistics exist for a table identified by the database query, and selecting a second optimization mode is selected if one or more statistics do not exist for the table identified by the database query, and wherein automatically tuning the selected database query comprises automatically rewriting the selected database query by converting the first operator to a second operator. 27. The system as recited in claim 26 , wherein the parsing determines tokens within the database query, tokens being words separated by delimiters.