Optimize toUpper & toLower
mark some functions to const
rename SQLTableColumn -> SQLTableCell, SQLTableHeaderColumn -> SQLTableHeader
implement getColumnIndexByName
fix memory leaking
separate execute counter
fix memory leak
added function doc
optimize memory cost
use SQLTable to store result in SQLResultObject
support print head columns
move xport to SQLTable
simplfy import and export
avoid copying in SQLResultObject
support concat integers and floats
more elegant error handling