在Activiti开发中，经常会产生大量垃圾数据，这时候就需要清理Activiti数据库，但是Activiti数据库中存在大量外键约束，所以就需要按顺序删除相关数据，具体顺序如下：

DELETE  FROM  act_hi_attachment;
DELETE  FROM  act_hi_comment;
DELETE  FROM  act_hi_detail;
DELETE  FROM  act_hi_actinst;
DELETE  FROM  act_hi_identitylink;
DELETE  FROM  act_hi_procinst;
DELETE  FROM  act_hi_taskinst;
DELETE  FROM  act_hi_varinst;
DELETE  FROM  act_ru_identitylink;
DELETE  FROM  act_ru_task;
DELETE  FROM  act_ru_variable;
DELETE  FROM  act_ru_execution WHERE PARENT_ID_ IS NOT NULL AND IS_SCOPE_=0;
DELETE  FROM  act_ru_execution WHERE PARENT_ID_ IS NOT NULL AND IS_SCOPE_=1;
DELETE  FROM  act_ru_execution;