進入sqlplus模式：sqlplusconn/assysdbaconnsys/123456asconnscott/tiger@orclconn

alteruserscottaccountunlock;alteruserscottaccountlock;注意：只有管理員才有權限和鎖定用戶！！！show查詢Scott用戶下empselect*fromDB：database數據庫DBMS：scott：createuserjava0408identifiedby修改：必須在cmd下面修改，在plsql中沒有效passwordJava0408刪除用戶:dropuserj0408cascade;cascade：創建的用戶任何權限【我們需要對用戶】角色：connectresourcedbagrantconnect,resource,dbatorevokeconnect,resourc,dbafromDMLI（ietinsertintoinsertintot_student(id,sname,age)values(11,'',25);commit;--提交insertintotableNameUPDATEupdate)age18updatet_studentsetage=18更新學生表中編號為1的學生的為20updatet_studentsetage=20whereid=1;DELETEdelete)語法deletefrom[where條件deletefromt_studentid3的記錄deletefromt_studentwhereid=3;truncatetablet_student4;select字段列表 [where查詢條件][groupby分組][having分組條件][orderby排序selectcount(*)fromt_studentselectcount(id)fromt_studentselectcount(cla)from--selectcount(1)fromselectid,sname,age,,cla,1,2,3fromt_studentselectsum(age)fromt_student;selectmin(age)fromt_student;selectmax(age)fromt_student;selectavg(age)fromselectconcat(id,sname)，length(sname)fromt_studentlower(str):str轉成小寫字符串字符串轉dateto_dateselect*fromt_studentaltertablet_studentaddbirth查詢當前時間selectsysdatefrom:selectsysdate,add_months(sysdate,-1fromdual;date轉字符串:to_charselectfromdual;selectadd_months(sysdate,12)fromdual;selectlast_day(sysdate)fromdual;nvl(column,value);null，就用默認值填充select ,'哈哈fromnvl2(column,v1,v2);null,就用v1填充，否則用v2select ,'不是空','是空fromdecode:類似于Javaif ,1,'男')-- ==1){男 ,1,'男','反正不是男的')-- ==1){男}else{反正不是男的 ,1,'男',2,'女if(){}else ,1,'男',2,'女','不詳')--if(){}elseif(){}else{}fromt_studentrownum:行號,系統自動的，從1開始自增，有1才有2selectt.*,rownumfromt_studentt5selectt.*,rownumfromt_studenttwhererownum510selectt.*,rownumfromt_studenttwhererownum>=5andrownum<=10selectt1.*,rownum(selectt.*,rownumnumfromt_studentt)t1wheret1.num>=5andt1.num<=10selectt2.*,rownum(selectt1.*,rownumnumfromt_studentt1whererownum<=10)t2wheret2.num>=5查詢出學生表中在【20歲以下【21-25【26以上】分別有多少selectcasewhenage20then1else0end21以下,casewhenage>20andage<26then1else0end"21-,casewhenage26then1else0end26以上"fromt_studenttsum(casewhenage20then1else0end21以下,sum(casewhenage>20andage<26then1else0end)"21-,sum(casewhenage26then1else0end26以上"fromt_studenttcount(casewhenage20then1elsenullend21以下,count(casewhenage>20andage<26then1elsenullend)"21-,count(casewhenage26then1elsenullend26以上"fromt_studenttselectt1.*,t2.*fromt_studentt1,t_class--交叉連接獲取的結果是一個乘selectt1.*,t2.*--100000 100Wwheret1.cla= --10selectfromt_studentt1innerjoint_classt2ont1.cla=selectfromt_classt2innerjoint_studentt1ont1.cla=--左邊的數據和右邊的數據滿足onselectt1.*,t2.*fromt_studentt1leftouterjoint_classt2ont1.cla=t2.cidselectfromt_classt1leftjoint_studentt2ont1.cid=t2.claselectt1.*,t2.*fromt_studentt1rightjoint_classt2ont1.cla=t2.cidselectt1.*,t2.*fromt_studentt1fulljoint_classt2ont1.cla=t2.cidselectid,name,cls_id,cls_name fromt_studentt1naturaljoint_classt2union和unionall關鍵字u