When a for statement is executed, a cursor is implicitly declared such that for each iteration of the for loop, the next row is the result set if fetched.
在执行for语句时，游标被隐式声明，这样对于FOR循环的每一次迭代，取回的下一行就是结果集。
2
You will recall that DataTables execute an implicit loop over their rows, and the var attribute indicates the value of the current row during the iteration.
您将再次调用 DataTables 对各表行执行隐式循环，var 属性指示迭代过程中的当前行。
3
On each iteration, db2_result gets the value for each field within the row.