一个非常好的ORACLE的分页SQL语句 select * from (select my_table.*, rownum as my_rownum from ( select yhbh, yhmc from yysf_tb_yonghxx order by yhbh) my_table where rownum <20 ) where my_rownum>=10------------------------------------其它几种分页实现:1.根据ROWID来分select * from t_xiaoxi where rowid in(select rid from (select rownum rn,rid from(select rowid rid,cid fromt_xiaoxi  order by cid desc) where rownum<10000) where rn>9980) order by cid desc;执行时间0.03秒2.按分析函数来分select * from (select t.*,row_number() over(order by cid desc) rk from t_xiaoxi t) where rk<10000 and rk>9980;执行时间1.01秒3.按ROWNUM来分select * from(select t.*,rownum rn from(select * from t_xiaoxi order by cid desc) t where rownum<10000) wherern>9980;执行时间0.1秒其中t_xiaoxi为表名称，cid为表的关键字段，取按CID降序排序后的第9981-9999条记录，t_xiaoxi表有70000多条记录个人感觉1的效率最好，3次之，2最差 oracle如何返回指定行数之间的查询结果如何返回指定行数之间的查询结果，以实现web记录分页，在Oracle中有许多的方法，这里仅仅列出了4种，希望能对大家有所帮助，大家可以根据不同需要选择下面的script　　　　　1）select ... where rownum < 50 minus select ... where rownum < 30　 　　　　这个方法因为用到了minus操作符，所以速度会受影响。　 　　2）　　　SELECT results.* FROM　 　　( SELECT t2.*, rownum rownumber FROM　 　　( SELECT t.* FROM mv_table t WHERE ORDER BY col1) t2) results　 　　WHERE results.rownumber BETWEEN 30 and 50 ORDER BY col1　　　这个方法是从一个论坛上看到的，没有亲自测试过　 　　3）　　　定义cursor x, 2.fetch x a,b,c; loop ...... end loop;　 　　其中用两个循环变量和一个FLAG变量，分别表示，当前的记录数，属于第几页的， 及第一页面。　 　　ps;　 　　j:=to_number(kafyf);　 　　i:=1;　 　　open cx;　 　　loop fetch cx into col1,col2,col3,col4,col5,col6;　 　　if cx%NOTFOUND then exit; end if;　 　　　　if i>=j then　 　　htp.tableRowOpen;　 　　htp.tableData(col1);　 　　htp.tableData(col2);　 　　htp.tableData(col4);　 　　htp.tableData(col5);　 　　htp.tableData(col6);　 　　htp.tableData(col3);　 　　htp.tableRowClose;　 　　i:=i+1;　 　　if i=j+10 then l:=1; exit; end if;　 　　else i:=i+1;　 　　end if;　 　　end loop;　 　　close x;　 　　该方法是名叫‘淼’的网友写的script，他用到了Oracle web2kit中的OWA_UTIL package。　　　　　4）How can one page forward and backwards through a table?　　　Externalize ROWNUM by implementing queries like this:　 　　　　SELECT ...　 　　FROM (SELECT ROWNUM rnum, ... FROM ...)　 　　WHERE rnum BETWEEN :low AND :high AND rownum <(:high :low + 1);　 　　　　where :low and :high are dynamically generated values depending on which result page the user　　　is viewing. Typically, they are used to show "Next 15 matches", "Previous 15 matches" links at the　　　bottom of each page.　 

Oracle高效的SQL语句之分析函数汇总分类： Oracle 2007-11-08 08:55 371人阅读 评论(0) 收藏 举报oraclesqltableinsertdate报表小毛头的BLOG[Oracle]高效的SQL语句之分析函数(一)--sum()  实际应用中我们可以通过sum()统计出组中的总计或者是累加值，具体示例如下：1.创建演示表create table empasselect * from scott.emp;alter table empadd constraint emp_pkprimary key(empno);create table deptasselect * from scott.dept;alter table deptadd constraint dept_pkprimary key(deptno);2. sum()语句如下：select deptno,       ename,       sal,　　--按照部门薪水累加（order by改变了分析函数的作用，只工作在当前行和前一行，而不是所有行）       sum(sal) over (partition by deptno order by sal) CumDeptTot,         sum(sal) over (partition by deptno) SalByDept,  --统计一个部门的薪水       sum(sal) over (order by deptno,sal) CumTot,  --所有雇员的薪水一行一行的累加       sum(sal) over () TotSal  --统计总薪水  from emp order by deptno, sal3. 结果如下：10    MILLER    1300.00    1300    8750    1300    2902510    CLARK    2450.00    3750    8750    3750    2902510    KING    5000.00    8750    8750    8750    2902520    SMITH    800.00    800    10875    9550    2902520    ADAMS    1100.00    1900    10875    10650    2902520    JONES    2975.00    4875    10875    13625    2902520    SCOTT    3000.00    10875    10875    19625    2902520    FORD    3000.00    10875    10875    19625    2902530    JAMES    950.00    950    9400    20575    2902530    WARD    1250.00    3450    9400    23075    2902530    MARTIN    1250.00    3450    9400    23075    2902530    TURNER    1500.00    4950    9400    24575    2902530    ALLEN    1600.00    6550    9400    26175    2902530    BLAKE    2850.00    9400    9400    29025    29025[Oracle]高效的SQL语句之分析函数(二)--max()如果我们按照示例想得到每个部门薪水值最高的雇员的纪录，可以有四种方法实现：先创建示例表create table empasselect * from scott.emp;alter table empadd constraint emp_pkprimary key(empno);create table deptasselect * from scott.dept;alter table deptadd constraint dept_pkprimary key(deptno);方法1.emp中的每一行都会进行max比较，费时select * from emp emp1 where emp1.sal=(select max(emp2.sal) from emp emp2 where emp2.deptno=emp1.deptno)方法2.先子查询查找出max sal，然后与emp表相关联，如果逻辑复杂会产生较多代码   select * from emp emp1,(select deptno,max(sal) maxsal from emp emp2 group by emp2.deptno) emp3 where emp1.deptno=emp3.deptno and emp1.sal=emp3.maxsal方法3.使用max分析函数select deptno,maxsal,empno from( select max(sal) over (partition by deptno) maxsal,emp.* from emp) emp2 where emp2.sal=emp2.maxsal方法4.使用dense_rank分析函数，如果一个部门可能存在多笔最大薪水，就不能使用row_number()分析函数select deptno,sal,empno from(  select emp.*,DENSE_RANK() over (partition by deptno order by sal desc) rownumber from emp) emp2 where rownumber=1 结果如下：10    5000.00    783920    3000.00    778820    3000.00    790230    2850.00    7698 [Oracle]高效的SQL语句之分析函数(三)--row_number() /rank()/dense_rank() 有些时候我们希望得到指定数据中的前n列，示例如下：得到每个部门薪水最高的三个雇员：先创建示例表create table empasselect * from scott.emp;alter table empadd constraint emp_pkprimary key(empno);create table deptasselect * from scott.dept;alter table deptadd constraint dept_pkprimary key(deptno);先看一下row_number() /rank()/dense_rank()三个函数之间的区别 select emp.deptno,emp.sal,emp.empno,row_number() over (partition by deptno order by sal desc) row_number,  --1,2,3  rank() over (partition by deptno order by sal desc) rank, --1,1,3  dense_rank() over (partition by deptno order by sal desc) dense_rank from emp --1,1,2结果如下:10    5000.00    7839    1    1    110    2450.00    7782    2    2    210    1300.00    7934    3    3    320    3000.00    7788    1    1    120    3000.00    7902    2    1    120    2975.00    7566    3    3    220    1100.00    7876    4    4    320    800.00    7369    5    5    430    2850.00    7698    1    1    130    1600.00    7499    2    2    2取每个部门的薪水前三位雇员：select t.deptno,t.rank,t.sal from ( select emp.*,row_number() over (partition by deptno order by sal desc) row_number,  --1,2,3  rank() over (partition by deptno order by sal desc) rank, --1,1,3  dense_rank() over (partition by deptno order by sal desc) dense_rank from emp --1,1,2 ) twhere t.rank<=3结果如下：10    1    5000.0010    2    2450.0010    3    1300.0020    1    3000.0020    1    3000.0020    3    2975.0030    1    2850.0030    2    1600.0030    3    1500.00如果想输出成deptno  sal1   sal2   sal3这种类型的格式步骤一（decode）：select t.deptno,decode(row_number,1,sal) sal1,decode(row_number,2,sal) sal2,decode(row_number,3,sal) sal3 from ( select emp.*,row_number() over (partition by deptno order by sal desc) row_number,  --1,2,3  rank() over (partition by deptno order by sal desc) rank, --1,1,3  dense_rank() over (partition by deptno order by sal desc) dense_rank from emp --1,1,2 ) twhere t.rank<=3结果如下：10    5000        10                  2450    10                             130020    3000        20                  3000    20                              297530    2850        30                 1600    30                             1500步骤二（使用聚合函数去除null,得到最终结果）：select t.deptno,max(decode(row_number,1,sal)) sal1,max(decode(row_number,2,sal)) sal2,max(decode(row_number,3,sal)) sal3 from ( select emp.*,row_number() over (partition by deptno order by sal desc) row_number,  --1,2,3  rank() over (partition by deptno order by sal desc) rank, --1,1,3  dense_rank() over (partition by deptno order by sal desc) dense_rank from emp --1,1,2 ) twhere t.rank<=3group by t.deptno 结果如下：10    5000    2450    130020    3000    3000    297530    2850    1600    1500 [Oracle]高效的SQL语句之分析函数(四)--lag()/lead()   有时候报表上面需要显示该笔操作的上一步骤或者下一步骤的详细信息，这个时候可以按照下面的做法：先创建示例表：-- Create tablecreate table LEAD_TABLE(  CASEID     VARCHAR2(10),  STEPID     VARCHAR2(10),  ACTIONDATE DATE)tablespace COLM_DATA  pctfree 10  initrans 1  maxtrans 255  storage  (    initial 64K    minextents 1    maxextents unlimited  );insert into LEAD_TABLE values(‘Case1‘,‘Step1‘,to_date(‘20070101‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case1‘,‘Step2‘,to_date(‘20070102‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case1‘,‘Step3‘,to_date(‘20070103‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case1‘,‘Step4‘,to_date(‘20070104‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case1‘,‘Step5‘,to_date(‘20070105‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case1‘,‘Step4‘,to_date(‘20070106‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case1‘,‘Step6‘,to_date(‘20070101‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case1‘,‘Step1‘,to_date(‘20070201‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case2‘,‘Step2‘,to_date(‘20070202‘,‘yyyy-mm-dd‘));insert into LEAD_TABLE values(‘Case2‘,‘Step3‘,to_date(‘20070203‘,‘yyyy-mm-dd‘));commit; 每一条记录都能连接到上/下一行的内容select caseid,stepid,actiondate,lead(stepid) over (partition by caseid order by actiondate) nextstepid,lead(actiondate) over (partition by caseid order by actiondate) nextactiondate,lag(stepid) over (partition by caseid order by actiondate) prestepid,lag(actiondate) over (partition by caseid order by actiondate) preactiondatefrom lead_table结果如下：Case1    Step1    2007-1-1    Step2    2007-1-2        Case1    Step2    2007-1-2    Step3    2007-1-3    Step1    2007-1-1Case1    Step3    2007-1-3    Step4    2007-1-4    Step2    2007-1-2Case1    Step4    2007-1-4    Step5    2007-1-5    Step3    2007-1-3Case1    Step5    2007-1-5    Step4    2007-1-6    Step4    2007-1-4Case1    Step4    2007-1-6    Step6    2007-1-7    Step5    2007-1-5Case1    Step6    2007-1-7                                       Step4    2007-1-6Case2    Step1    2007-2-1    Step2    2007-2-2        Case2    Step2    2007-2-2    Step3    2007-2-3    Step1    2007-2-1Case2    Step3    2007-2-3                                       Step2    2007-2-2 还可以进一步统计一下两者的相差天数select caseid,stepid,actiondate,nextactiondate,nextactiondate-actiondate datebetween from (select caseid,stepid,actiondate,lead(stepid) over (partition by caseid order by actiondate) nextstepid,lead(actiondate) over (partition by caseid order by actiondate) nextactiondate,lag(stepid) over (partition by caseid order by actiondate) prestepid,lag(actiondate) over (partition by caseid order by actiondate) preactiondatefrom lead_table) 结果如下：Case1    Step1    2007-1-1    2007-1-2    1Case1    Step2    2007-1-2    2007-1-3    1Case1    Step3    2007-1-3    2007-1-4    1Case1    Step4    2007-1-4    2007-1-5    1Case1    Step5    2007-1-5    2007-1-6    1Case1    Step4    2007-1-6    2007-1-7    1Case1    Step6    2007-1-7        Case2    Step1    2007-2-1    2007-2-2    1Case2    Step2    2007-2-2    2007-2-3    1Case2    Step3    2007-2-3