[摘要] 今天在查詢一個菜單的所有父菜單的時候，報(bào)“ORA-01436: 用戶數(shù)據(jù)中的 CONNECT BY 循環(huán) ”錯誤，所用SQL如下：select * from roles m start with m.rno=690702 connect by prior m.r_rno=m.rno;仔細(xì)...[全文]
[摘要] 創(chuàng)建測試數(shù)據(jù)創(chuàng)建db:testdb,collection:user,插入10條記錄mongoMongoDB shell version: 3.0.2connecting to: test> use testdbswitched to db testdb> db.user.insert({id:1,n[全文]
[摘要] 從一次查詢中隨機(jī)返回一條數(shù)據(jù)，一般使用mysql的order by rand() 方法來實(shí)現(xiàn)例如: 從20萬用戶中隨機(jī)抽取1個用戶mysql> select * from user order by rand() limit 1;+-------+------------+---------...[全文]
