No, depending on the complexity of your process you will have multiple executions (eg for each parallel path, for each scope, ect.) as child of the process instance or even nested.
also (iirc) TaskIds can also be refered as an Execution id, because tasks AND Processes are Executions. (check act_ru_executions - There you find Tasks, Processes, signals, gateways, …)
@Donose: Tasks are NOT executions and have their own table (ACT_RU_TASK). If you have a task with a boundary-event, there will indeed be an additional execution in the ACT_RU_EXECUTION table, but this is an extra scope around the user task, and not the task itself…
