本系列链接导航：
[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
declare
cursor myCursor is
select name from person;
vNames varchar2(128);
begin
--遍历游标
for c in myCursor loop --隐式打开、关闭游标
vNames:=vNames||','||c; -- 可以包含复杂逻辑
end loop;
end;
- 显示游标
declare
cursor myCursor is --定义游标
select * from person;
my_c myCursor%rowtype --定义游标变量
begin
open myCursor;
loop
fetch myCursor into my_c;
exit when c%notfound;
/*code here*/ --编写复杂逻辑
end loop; Exception
when others then
close myCursor; if myCursor%isopen then
close myCursor;
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;
declare
---define Cursor
Cursor cur_policy is
select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,cm.bank_account
from t_contract_master cm
where cm.liability_state = 2
and cm.policy_type = 1
and cm.policy_cate in ('','','')
and rownum < 5
order by cm.policy_code desc;
curPolicyInfo cur_policy%rowtype;---定义游标变量
Begin
open cur_policy; ---open cursor
Loop
--deal with extraction data from DB
Fetch cur_policy into curPolicyInfo;
Exit when cur_policy%notfound; Dbms_Output.put_line(curPolicyInfo.policy_code);
end loop;
Exception
when others then
close cur_policy;
Dbms_Output.put_line(Sqlerrm); if cur_policy%isopen then
--close cursor
close cur_policy;
end if;
end; /
2） Set serveroutput on;
declare
Cursor cur_policy is
select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,cm.bank_account
from t_contract_master cm
where cm.liability_state = 2
and cm.policy_type = 1
and cm.policy_cate in ('','','')
and rownum < 5
order by cm.policy_code desc;
v_policyCode t_contract_master.policy_code%type;
v_applicantId t_contract_master.applicant_id%type;
v_periodPrem t_contract_master.period_prem%type;
v_bankCode t_contract_master.bank_code%type;
v_bankAccount t_contract_master.bank_account%type;
Begin
open cur_policy;
Loop
Fetch cur_policy into v_policyCode,
v_applicantId,
v_periodPrem,
v_bankCode,
v_bankAccount;
Exit when cur_policy%notfound; Dbms_Output.put_line(v_policyCode);
end loop;
Exception
28 when others then
close cur_policy;
Dbms_Output.put_line(Sqlerrm); if cur_policy%isopen then
close cur_policy;
end if;
end;
/
3）Set serveroutput on;
declare
Cursor cur_policy is
select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,cm.bank_account
from t_contract_master cm
where cm.liability_state = 2
and cm.policy_type = 1
and cm.policy_cate in ('','','')
and rownum < 5
order by cm.policy_code desc;
Begin
For rec_Policy in cur_policy loop
Dbms_Output.put_line(rec_policy.policy_code);
end loop;
Exception
when others then
Dbms_Output.put_line(Sqlerrm); end; /
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
Declare
---define cursor type name
type cur_type is ref cursor;
cur_policy cur_type;
sqlStr varchar2(500);
rec_policy t_contract_master%rowtype;
begin
---define 动态Sql
sqlStr := 'select cm.policy_code, cm.applicant_id, cm.period_prem,cm.bank_code,
cm.bank_account from t_contract_master cm
where cm.liability_state = 2
and cm.policy_type = 1
and cm.policy_cate in (2,3,4)
and rownum < 5
order by cm.policy_code desc ';
---Open Cursor
open cur_policy for sqlStr;
loop
fetch cur_policy into rec_policy.policy_code, rec_policy.applicant_id, rec_policy.period_prem,
rec_policy.bank_code,rec_policy.bank_account;
exit when cur_policy%notfound; Dbms_Output.put_line('Policy_code:'||rec_policy.policy_code); end loop;
close cur_policy; end;
/
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。