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[独孤九剑]Oracle知识点梳理(七)数据库常用对象之Cursor

时间:2015-03-15 23:40:36      阅读:316      评论:0      收藏:0      [点我收藏+]

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本系列链接导航:

[独孤九剑]Oracle知识点梳理(一)表空间、用户

[独孤九剑]Oracle知识点梳理(二)数据库的连接

[独孤九剑]Oracle知识点梳理(三)导入、导出

[独孤九剑]Oracle知识点梳理(四)SQL语句之DML和DDL

[独孤九剑]Oracle知识点梳理(五)数据库常用对象之Table、View

[独孤九剑]Oracle知识点梳理(六)数据库常用对象之Procedure、function、Sequence

[独孤九剑]Oracle知识点梳理(七)数据库常用对象之Cursor

[独孤九剑]Oracle知识点梳理(八)常见Exception 

[独孤九剑]Oracle知识点梳理(九)数据库常用对象之package

[独孤九剑]Oracle知识点梳理(十)%type与%rowtype及常用函数

5.6、cursor操作

  游标的使用场景大致有:

    a) 显示游标:function或procedure中,用于获取某些值进行遍历操作

    b) 动态游标:procedure中,用于返回查询结果

5.6.1、显示游标:在代码段、function、procdeure中创建cursor,用于取值

  • 隐式游标
 1 declare 
 2     cursor myCursor is
 3         select name from person;
 4   vNames varchar2(128);
 5 begin 
 6   --遍历游标
 7   for c in myCursor loop --隐式打开、关闭游标
 8     vNames:=vNames||,||c; -- 可以包含复杂逻辑
 9   end loop;    
10 end;    
  • 显示游标
 1 declare 
 2   cursor myCursor is    --定义游标
 3     select * from person;
 4   my_c myCursor%rowtype    --定义游标变量
 5 begin 
 6   open myCursor;
 7   loop
 8     fetch myCursor into my_c;
 9     exit when c%notfound;
10     /*code here*/ --编写复杂逻辑
11   end loop;
12 
13   Exception 
14     when others then 
15       close myCursor;
16 
17 
18   if myCursor%isopen then
19     close myCursor;
20 end;

  上面写的两个列子比较简单,下面是网上摘抄显示游标例子,很详细:

  对于显式游标的运用分为四个步骤:

  • 定义游标---Cursor [Cursor Name] IS;
  • 打开游标---Open [Cursor Name];
  • 操作数据---Fetch [Cursor name]
  • 关闭游标---Close [Cursor Name],这个Step绝对不可以遗漏。

  以下是三种常见显式Cursor用法。
1)Set serveroutput on;

 1 declare 
 2   ---define Cursor 
 3   Cursor cur_policy is 
 4     select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,cm.bank_account 
 5         from t_contract_master cm 
 6         where cm.liability_state = 2 
 7             and cm.policy_type = 1 
 8             and cm.policy_cate in (2,3,4) 
 9             and rownum < 5 
10         order by cm.policy_code desc; 
11   curPolicyInfo cur_policy%rowtype;---定义游标变量 
12 Begin 
13   open cur_policy; ---open cursor 
14   Loop 
15     --deal with extraction data from DB 
16     Fetch cur_policy into curPolicyInfo; 
17     Exit when cur_policy%notfound; 
18 
19     Dbms_Output.put_line(curPolicyInfo.policy_code); 
20   end loop; 
21   Exception 
22     when others then 
23       close cur_policy; 
24     Dbms_Output.put_line(Sqlerrm); 
25 
26   if cur_policy%isopen then 
27     --close cursor 
28     close cur_policy; 
29   end if; 
30 end; 
31 
32 /

2) Set serveroutput on; 

 1 declare 
 2   Cursor cur_policy is 
 3     select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,cm.bank_account 
 4       from t_contract_master cm 
 5       where cm.liability_state = 2 
 6         and cm.policy_type = 1 
 7         and cm.policy_cate in (2,3,4) 
 8         and rownum < 5 
 9       order by cm.policy_code desc; 
10   v_policyCode t_contract_master.policy_code%type; 
11   v_applicantId t_contract_master.applicant_id%type; 
12   v_periodPrem t_contract_master.period_prem%type; 
13   v_bankCode t_contract_master.bank_code%type; 
14   v_bankAccount t_contract_master.bank_account%type; 
15 Begin 
16   open cur_policy; 
17   Loop 
18     Fetch cur_policy into v_policyCode, 
19                 v_applicantId, 
20                 v_periodPrem, 
21                 v_bankCode, 
22                 v_bankAccount; 
23     Exit when cur_policy%notfound; 
24 
25     Dbms_Output.put_line(v_policyCode); 
26   end loop; 
27   Exception 
28    when others then 
29       close cur_policy; 
30     Dbms_Output.put_line(Sqlerrm); 
31 
32   if cur_policy%isopen then 
33     close cur_policy; 
34   end if; 
35 end; 
36 /

3)Set serveroutput on; 

 1 declare 
 2   Cursor cur_policy is 
 3     select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,cm.bank_account 
 4         from t_contract_master cm 
 5         where cm.liability_state = 2 
 6           and cm.policy_type = 1 
 7           and cm.policy_cate in (2,3,4) 
 8           and rownum < 5 
 9         order by cm.policy_code desc; 
10 Begin 
11   For rec_Policy in cur_policy loop 
12     Dbms_Output.put_line(rec_policy.policy_code); 
13   end loop; 
14   Exception 
15     when others then 
16     Dbms_Output.put_line(Sqlerrm); 
17 
18 end; 
19 
20 / 

5.6.2、动态游标:在procdeure中使用cursor,用于返回查询结果

  与隐式Cursor,显式Cursor的区别:

  • Ref Cursor是可以通过在运行期间传递参数来获取数据结果集。
  • 而另外两种Cursor(隐式游标和显示游标),是静态的,在编译期间就决定数据结果集。

5.6.2.1、定义动态游标

 1 Declare
 2   ---define cursor type name 
 3   type cur_type is ref cursor; 
 4   cur_policy cur_type; 
 5   sqlStr varchar2(500); 
 6   rec_policy t_contract_master%rowtype; 
 7 begin 
 8   ---define 动态Sql 
 9   sqlStr := select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,
              cm.bank_account from t_contract_master cm
10           where cm.liability_state = 2 11               and cm.policy_type = 1 12               and cm.policy_cate in (2,3,4) 13               and rownum < 5 14             order by cm.policy_code desc ; 15   ---Open Cursor 16   open cur_policy for sqlStr; 17   loop 18     fetch cur_policy into rec_policy.policy_code, rec_policy.applicant_id, rec_policy.period_prem,
                  rec_policy.bank_code,rec_policy.bank_account;
19     exit when cur_policy%notfound; 20 21     Dbms_Output.put_line(Policy_code:||rec_policy.policy_code); 22 23   end loop; 24 close cur_policy; 25 26 end; 27 /

另外,在定义package时,可以在包头中定义动态游标类型,在包体中使用,如在procedure中用于定义返回参数类型。详见package的操作。

[独孤九剑]Oracle知识点梳理(七)数据库常用对象之Cursor

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原文地址:http://www.cnblogs.com/cloud915/p/4340733.html

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