2) 常用预定义例外
  EXCEPTION
    WHEN CURSOR_ALREADY_OPEN THEN -- ORA-06511 SQLCODE = -6511 游标已经打开
      ...
    WHEN DUP_VAL_ON_INDEX THEN -- ORA-00001 SQLCODE = -1 向唯一索引中插入重复数据
      ...
    WHEN INVALID_CURSOR THEN -- ORA-01001 SQLCODE = -1001 非法游标操作
      ...
    WHEN INVALID_NUMBER THEN -- ORA-01722 SQLCODE = -1722 字符向数字转换失败
      ...
    WHEN LOGIN_DENIED THEN -- ORA-01017 SQLCODE = -1017
      ...
    WHEN NO_DATA_FOUND THEN -- ORA-01403 SQLCODE = +100 没有找到数据
      ...
    WHEN NOT_LOGGED_ON THEN -- ORA-01012 SQLCODE = -1012
      ...
    WHEN PROGRAM_ERROR THEN -- ORA-06501 SQLCODE = -6501 程序错误
      ...
    WHEN STORAGE_ERROR THEN -- ORA-06500 SQLCODE = -6500
      ...
    WHEN TIMEOUT_ON_RESOURCE THEN -- ORA-00051 SQLCODE = -51
      ...
    WHEN TOO_MANY_ROWS THEN -- ORA-01422 SQLCODE = -1422 返回多行
      ...
    WHEN TRANSACTION_BACKED_OUT THEN -- ORA-00061 SQLCODE = -61
      ...
    WHEN VALUE_ERROR THEN -- ORA-06502 SQLCODE = -6502 数值转换错误
      ...
    WHEN ZERO_DIVIDE THEN -- ORA-01476 SQLCODE = -1476 被零除
      ...
    WHEN OTHERS THEN -- 其它任何错误的处理
      ...
  END;

  3) 用户定义的例外
  DECLARE
    FIND_DATA_EMP    EXCEPTION;
  BEGIN
    IF ... THEN
      RAISE FIND_DATA_EMP;
    END IF;
  EXCEPTION
    WHEN LOB_NO_LOCKED THEN
      ...
  END;
  4) EXCEPTION_INIT的使用
  PRAGMA EXCEPTION_INIT(例外名, ORACLE错误号);
  注：PRAGMA 是一个编译器命令，可以认为是对编译器的一个注释。
  例：
  DECLARE
    ZERO_DIVIDE1    EXCEPTION;
    PRAGMA EXCEPTION_INIT(ZERO_DIVIDE1, -1476);
  BEGIN
    ...
  EXCEPTION
    WHEN ZERO_DIVIDE1 THEN
      ...
  END;

第一种

select cname from col where tname='EMP';

第二种

select column_name from user_tab_columns where table_name='EMP';

介绍  如果查询数据的  字段数据类型

select data_type from user_tab_columns where table_name='EMP';

两个一起查

select data_type,column_name from user_tab_columns where table_name='EMP';

--------------------------------------------查询 字段注释---------------------------------------------

select * from user_col_comments ;//所有的注释
select * from user_col_comments where table_name='你的表(emp)' ;//指定表的注释

--用Sample：
select A.id,A.name from A sample block(20),B 
where A.id=B.id
--用Rownum：
select A.id,A.name from (select a.id,a.name from a where rownum<100) A,B 
where A.id=B.id

抽样表扫描有两种形式，一种是抽样表中行数的一个百分比，一个是抽样表中块数的一个百分比。注意都是百分比。语法如下：

SELECT * FROM employees SAMPLE (1);--返回行数乘以1%
SELECT * FROM employees SAMPLE BLOCK (1);--返回块数乘以1%

也可以在视图上使用SAMPLE。

--好像只能恢复当日删除的数据
create table t_hjhb_hbjcjl2 as
select * from t_hjhb_hbjcjl as of timestamp to_timestamp('2009-06-10 10:28:00','YYYY-MM-DD HH24:MI:SS');

查找要恢复的数据记录；然后再导入t_hjhb_hbjcjl表里
insert into t_hjhb_hbjcjl select * from t_hjhb_hbjcjl2

两张表关联更新另一张表的字段：
update atest
set (name,name2) = (SELECT CASE WHEN CTEST.NAME IS NULL THEN ATEST.NAME ELSE CTEST.NAME END, CASE WHEN CTEST.NAME2 IS NULL THEN ATEST.NAME2 ELSE CTEST.NAME2 END FROM BTEST LEFT JOIN CTEST on BTEST.ID = CTEST.ID  WHERE atest.CODE = BTEST.CODE)
WHERE atest.CODE IN (SELECT BTEST.CODE FROM BTEST);


另外一个: http://blog.csdn.net/Bobwu/archive/2009/01/13/3768636.aspx
1.
declare
cursor t1 is select * from tablename;
begin
for rec in t1 loop
update tablename t set t.detail=rec.jieshao where t.objectid=rec.objid;
end loop;
end;

2.

update   student   set   (name,id   )=  
  (select   name   ,id     from   (select   student.rowid   rd,student1.name,student1.id   from   student1,student   where   student1.int_id   =student.int_id)   tmp  
  where   student.rowid=tmp.rd);  
  commit;

3.

update test_a a set (a.name,a.age)=
(select b.name,b.age from test_b b where a.id = b.id) where exists
(select * from test_b c where c.id=a.id)

4.

UPDATE   t_A   SET   Djrq=    
  (  
          SELECT   djrq   FROM   t_B   WHERE   t_A.ID   =   T_B.ID    
          WHERE   ROWNUM   =   1    
  )  
  WHERE   t_A.ID   IN    
  (  
          SELECT   ID   FROM   t_B   WHERE   jwh='XX村'  
  )

5.

update tbl1 a
   set (a.col1, a.col2) = (select b.col1, b.col2
                              from tbl2 b
                              where a.key = b.key)
   where a.key in(select key from tbl2)

   IF the_ratio > lower_limit THEN
      INSERT INTO ratio VALUES (samp_num, the_ratio);
   ELSE
      INSERT INTO ratio VALUES (samp_num, -1);
   END IF;
   COMMIT;
EXCEPTION
   WHEN ZERO_DIVIDE THEN
      INSERT INTO ratio VALUES (samp_num, 0);
      COMMIT;
   WHEN OTHERS THEN
      ROLLBACK;
END;

2.
CREATE OR REPLACE PROCEDURE
    get_student_major
        (v_student_id  IN  students.student_id%TYPE,
         v_name        OUT students.student_name%TYPE) IS
BEGIN
    SELECT student_name
      INTO v_name
      FROM students
     WHERE student_id = v_student_id;
exception
    WHEN TOO_MANY_ROWS THEN dbms_output.put_line('TMR error'); -- 行数 > 1
    WHEN NO_DATA_FOUND THEN dbms_output.put_line('NDF error'); -- 行数为 0
END;

3.
CREATE OR REPLACE FUNCTION
    update_salaries(new_sal IN professors.salary%TYPE) -- %TYPE 某一字段的类型作为类型
    RETURN NATURAL IS
BEGIN
    UPDATE professors2 SET salary = new_sal;
    RETURN SQL%ROWCOUNT; -- 判断更新的行数
END update_salaries;

4.
CREATE OR REPLACE PROCEDURE
    add_student(rec IN OUT students%ROWTYPE) IS -- students%ROWTYPE作为表的某一行作为变量类型
BEGIN
    SELECT 'A'||students_pk_seq.nextval
      INTO rec.student_id
      FROM dual;

    INSERT INTO students (student_id, student_name,
        college_major, status, state, license_no)
    VALUES (rec.student_id, rec.student_name,
        rec.college_major, rec.status,
        rec.state, rec.license_no);
END add_student;

5.
DECLARE
   dept_rec1 dept%ROWTYPE;  --dept是表名,则dept_rec1 和 dept_rec2 可以相互赋值
   dept_rec2 dept%ROWTYPE;

   CURSOR c1 IS SELECT deptno, dname, loc FROM dept;
   dept_rec3 c1%ROWTYPE;
BEGIN
   ...
   dept_rec1 := dept_rec2;

However, because dept_rec2 is based on a table and dept_rec3 is based on a cursor, the following assignment is illegal:
dept_rec2 := dept_rec3;  -- illegal

6.
DECLARE
   CURSOR my_cursor IS
      SELECT sal + NVL(comm, 0) wages, ename FROM emp;
   my_rec  my_cursor%ROWTYPE;
BEGIN
   OPEN my_cursor;
   LOOP
      FETCH my_cursor INTO my_rec;
      EXIT WHEN my_cursor%NOTFOUND;

      IF my_rec.wages > 2000 THEN
         INSERT INTO temp VALUES (NULL, my_rec.wages, my_rec.ename);
      END IF;
   END LOOP;
   CLOSE my_cursor;
END;

7. *****
-- 包，函数，存储过程
CREATE OR REPLACE PACKAGE BODY students_pkg IS

    FUNCTION add_student(rec IN students%ROWTYPE)
        RETURN students.student_id%TYPE
    IS
        ID students.student_id%TYPE;
    BEGIN
        SELECT 'A'||students_pk_seq.nextval INTO ID FROM dual;

        INSERT INTO students (student_id, student_name,
            college_major, status, state, license_no)
        VALUES (ID, rec.student_name, rec.college_major,
            rec.status, rec.state, rec.license_no);

        RETURN ID;
    END add_student;

    PROCEDURE add_vehicle(rec IN student_vehicles%ROWTYPE) IS
    BEGIN
        INSERT INTO student_vehicles (state, tag_no,
            vehicle_desc, student_id, parking_sticker)
        VALUES (rec.state, rec.tag_no,
            rec.vehicle_desc, rec.student_id, rec.parking_sticker);
    END add_vehicle;
END students_pkg;

-- 执行
DECLARE
    student students%ROWTYPE;
    vehicle student_vehicles%ROWTYPE;
BEGIN
    student.student_name  := 'Jack';
    student.college_major := 'HI';
    student.status        := 'Degree';
    student.state         := 'CA';
    student.license_no    := 'MV-232-14';

    student.student_id := students_pkg.add_student(student);

    vehicle.state           := 'CA';
    vehicle.tag_no          := 'CA-1234';
    vehicle.vehicle_desc    := 'Mustang';
    vehicle.parking_sticker := 'A-101';

    vehicle.student_id := student.student_id;

    students_pkg.add_vehicle(vehicle);
END;

2.答案如下：
select name,sum(yuwen) yuwen,sum(shuxue)  shuxue,sum(huaxue)  huaxue
from(
    select name,
       case kechen when '语文' then fengshu end yuwen,
    case kechen when '数学' then fengshu end shuxue,
    case kechen when '化学' then fengshu end huaxue
    from table
 )as t1
group by name

2、删除表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断，只留有rowid最小的记录
delete from people
where peopleId in (select   peopleId from people group by   peopleId   having count (peopleId) > 1)
and rowid not in (select min(rowid) from   people group by peopleId having count(peopleId )>1)

3、查找表中多余的重复记录（多个字段）
select * from vitae a
where (a.peopleId,a.seq) in   (select peopleId,seq from vitae group by peopleId,seq having

count(*) > 1)

4、删除表中多余的重复记录（多个字段），只留有rowid最小的记录
delete from vitae a
where (a.peopleId,a.seq) in   (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

5、查找表中多余的重复记录（多个字段），不包含rowid最小的记录
select * from vitae a
where (a.peopleId,a.seq) in   (select peopleId,seq from vitae group by peopleId,seq having

count(*) > 1)
and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

(二)
比方说
在A表中存在一个字段“name”，
而且不同记录之间的“name”值有可能会相同，
现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；
Select Name,Count(*) From A Group By Name Having Count(*) > 1
如果还查性别也相同大则如下:
Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

(三)
方法一
declare @max integer,@id integer
declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having

count(*) >； 1
open cur_rows
fetch cur_rows into @id,@max
while @@fetch_status=0
begin
select @max = @max -1
set rowcount @max
delete from 表名 where 主字段 = @id
fetch cur_rows into @id,@max
end
close cur_rows
set rowcount 0

方法二

有两个意义上的重复记录，一是完全重复的记录，也即所有字段均重复的记录，

二是部分关键字段重复的记录，比如Name字段重复，而其他字段不一定重复或都重复可以忽略。

　　1、对于第一种重复，比较容易解决，使用
select distinct * from tableName

　　就可以得到无重复记录的结果集。

　　如果该表需要删除重复的记录（重复记录保留1条），可以按以下方法删除
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp

　　发生这种重复的原因是表设计不周产生的，增加唯一索引列即可解决。

　　2、这类重复问题通常要求保留重复记录中的第一条记录，操作方法如下

　　假设有重复的字段为Name,Address，要求得到这两个字段唯一的结果集
select identity(int,1,1) as autoID, * into #Tmp from tableName
select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID
select * from #Tmp where autoID in(select autoID from #tmp2)

　　最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写

在select子句中省去此列）

(四)查询重复
select * from tablename

where id in (select id from tablename group by id having count(id) > 1)

(五)删除重复
delete from test a where a.rowid !=
 ( select max(b.rowid) from test b where a.id = b.id  )

(六)删除重复
方法一：delete from demo a where a.rowid <> (select max(rowid) from demo b where
b.object_id=a.object_id);
耗时：几个小时以上
方法二： delete from demo where rowid in
(select rid from
(select rowid rid,row_number() over(partition by object_id order by rowid) rn
from demo)
where rn <> 1 );
耗时：30秒
方法三： create table demo2 as
select object_id,owner... from
(select demo.*,row_number() over(partition by object_id order by rowid) rn from demo)
where rn = 1;
truncate table demo; insert into demo select * from demo2; drop table demo2;
共耗时： 10秒，适合大数据量的情况，产生更少回滚量；