Design and implementation of SQL builder

Writing complicated SQL statement needs lots of time and is easy to make mistakes.So many SQL builders are designed,but some of which have no ability of mistake-checking and good extensibility.Select_SQL_Builder is designed on the basis of the ad-vantage of existing SQL builders,which is based on SQL92 standards and the most complicated select statement can be realized.The integrity,repeatability and type matching of SQL statement are checked via the system.In order to display,modify,check and build SQL statement,function,expression and condition are defined as object.Furthermore,the change database is changed easy,delete statement and update statement are realized with a little modification.