The script assigns a value to the global variablebound to the computed field.
脚本将值指定给绑定到computed字段的全局变量。
2
Once an application variable is bound to a parameter marker, the association remains until it is overridden or until the corresponding statement handle is freed.
一旦应用程序变量被绑定到某个参数标记，这种关联就会一直保持下去，直到相应的语句句柄被释放。
3
When the graph keyword is used with a graph's URI (or a variable already bound to a graph's URI), the graph pattern is applied to whichever graph is identified by that URI.