http://www.cs.uoi.gr/~pitoura/informix-doc/
http://www.cs.uoi.gr/~pitoura/informix-doc/SQL_Quick_Syntax_Guide.pdf
http://www.cs.uoi.gr/~pitoura/informix-doc/Informix_Guide_to_SQL-Tutorial.pdf
http://www.cs.uoi.gr/~pitoura/informix-doc/Informix_Guide_to_SQL-Syntax.pdf
https://download.csdn.net/download/vincent371215/3838686