oracle的cursor的介紹

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一? 概念
???? 游標是SQL的一個內存工作區，由系統或用戶以變量的形式定義。

游標的作用就是用于臨時存儲從數據庫中提取的數據塊。在某些情況下，需要把數據從存放在磁盤的表中調到計算機內存中進行處理，最后將處理結果顯示出來或最終寫回數據庫。這樣數據處理的速度才會提高，否則頻繁的磁盤數據交換會降低效率。
二? 類型
? ???Cursor類型包含三種: 隱式Cursor，顯式Cursor和Ref Cursor（動態Cursor）。
1．隱式Cursor:
??? 1)對于select …into…語句，一次只能從數據庫中獲取到一條數據，對于這種類型的DML Sql語句，就是隱式Cursor。

例如：Select /Update / Insert/Delete操作。
2)作用：可以通過隱式Cusor的屬性來了解操作的狀態和結果，從而達到流程的控制。Cursor的屬性包含：
??? SQL%ROWCOUNT 整型 代表DML語句成功執行的數據行數
??? SQL%FOUND? 布爾型? 值為TRUE代表插入、刪除、更新或單行查詢操作成功
??? SQL%NOTFOUND 布爾型 與SQL%FOUND屬性返回值相反
??? SQL%ISOPEN 布爾型 DML執行過程中為真，結束后為假
3) 隱式Cursor是系統自動打開和關閉Cursor.
下面是一個Sample：

Sql代碼

1.?? Set?Serveroutput?on; ??

2.?? ??

3.?? begin??

4.?? ????update?t_contract_master?set?liability_state?=?1?where?policy_code?=?'123456789'; ??

5.?? ???? ??

6.?? ????if?SQL%Found?then??

7.?? ???????dbms_output.put_line('the?Policy?is?updated?successfully.'); ??

8.?? ???????commit; ??

9.?? ????else??

10.? ??????dbms_output.put_line('the?policy?is?updated?failed.'); ??

11.? ????end?if; ????

12.? end; ????

13.? /??

Set Serveroutput on;

?

begin

??? update t_contract_master set liability_state = 1 where policy_code = '123456789';

???

??? if SQL%Found then

?????? dbms_output.put_line('the Policy is updated successfully.');

?????? commit;

??? else

????? dbms_output.put_line('the policy is updated failed.');

??? end if;

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end;

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/

在PL/SQL中run:

Sql代碼

1.?? SQL>? ??? ??

2.?? the?policy?is?updated?failed. ??? ??

3.? PL/SQL?procedure?successfully?completed??

SQL>

?

the policy is updated failed.

?

PL/SQL procedure successfully completed

2． 顯式Cursor：
(1)對于從數據庫中提取多行數據，就需要使用顯式Cursor。顯式Cursor的屬性包含：
??? 游標的屬性?? 返回值類型??? 意 義?
???? %ROWCOUNT?? 整型???????? ?獲得FETCH語句返回的數據行數?
???? %FOUND? ????布爾型 ???????最近的FETCH語句返回一行數據則為真，否則為假?
???? %NOTFOUND?? 布爾型 ???????與%FOUND屬性返回值相反?
???? %ISOPEN ????布爾型 ???????游標已經打開時值為真，否則為假?

(2)對于顯式游標的運用分為四個步驟：
?????? ?定義游標---Cursor? [Cursor Name]? IS;ü
?????? ?打開游標---Open?ü [Cursor Name];
??????? 操作數據---Fetch? [Cursor name]ü
?????? ?關閉游標---Close [Cursorü Name],這個Step絕對不可以遺漏。
(3)以下是三種常見顯式Cursor用法。
1）

Sql代碼

1.?? Set?serveroutput?on; ??

2.?? ??

3.?? declare? ??

4.?? ????---define?Cursor ??

5.?? ????Cursor?cur_policy?is??

6.?? ?????select?cm.policy_code,?cm.applicant_id,?cm.period_prem,cm.bank_code,cm.bank_account ??

7.?? ?????from?t_contract_master?cm ??

8.?? ?????where?cm.liability_state?=?2 ??

9.?? ?????and?cm.policy_type?=?1 ??

10.? ?????and?cm.policy_cate?in?('2','3','4') ??

11.? ?????and?rownum?<?5 ??

12.? ?????order?by?cm.policy_code?desc; ??

13.? ????curPolicyInfo?cur_policy%rowtype;---定義游標變量 ??

14.? Begin??

15.? ???open?cur_policy;?---open?cursor ??

16.? ???Loop? ??

17.? ?????--deal?with?extraction?data?from?DB ??

18.? ?????Fetch?cur_policy?into?curPolicyInfo; ??

19.? ?????Exit?when?cur_policy%notfound; ??

20.? ????????? ??

21.? ?????Dbms_Output.put_line(curPolicyInfo.policy_code); ??

22.? ???end?loop; ??

23.? ???Exception? ??

24.? ?????when?others?then??

25.? ?????????close?cur_policy; ??

26.? ?????????Dbms_Output.put_line(Sqlerrm); ??????????? ??

27.? ???if?cur_policy%isopen?then?? ??

28.? ????--close?cursor? ??

29.? ??????close?cur_policy; ??

30.? ???end?if; ??

31.? end; ????

32.? /??

Set serveroutput on;

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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 ('2','3','4')

???? and rownum < 5

???? order by cm.policy_code desc;

??? curPolicyInfo cur_policy%rowtype;---定義游標變量

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）

Sql代碼

1.?? Set?serveroutput?on; ??

2.?? ??

3.?? declare? ??

4.?? ????Cursor?cur_policy?is??

5.?? ?????select?cm.policy_code,?cm.applicant_id,?cm.period_prem,cm.bank_code,cm.bank_account ??

6.?? ?????from?t_contract_master?cm ??

7.?? ?????where?cm.liability_state?=?2 ??

8.?? ?????and?cm.policy_type?=?1 ??

9.?? ?????and?cm.policy_cate?in?('2','3','4') ??

10.? ?????and?rownum?<?5 ??

11.? ?????order?by?cm.policy_code?desc; ??

12.? ?????v_policyCode?t_contract_master.policy_code%type; ??

13.? ?????v_applicantId?t_contract_master.applicant_id%type; ??

14.? ?????v_periodPrem?t_contract_master.period_prem%type; ??

15.? ?????v_bankCode?t_contract_master.bank_code%type; ??

16.? ?????v_bankAccount?t_contract_master.bank_account%type; ??

17.? Begin??

18.? ???open?cur_policy; ??

19.? ???Loop? ??

20.? ?????Fetch?cur_policy?into?v_policyCode, ??

21.? ???????????????????????????v_applicantId, ??

22.? ???????????????????????????v_periodPrem, ??

23.? ???????????????????????????v_bankCode, ??

24.? ???????????????????????????v_bankAccount; ??

25.? ?????Exit?when?cur_policy%notfound; ??

26.? ????????? ??

27.? ?????Dbms_Output.put_line(v_policyCode); ??

28.? ???end?loop; ??

29.? ???Exception? ??

30.? ?????when?others?then??

31.? ?????????close?cur_policy; ??

32.? ?????????Dbms_Output.put_line(Sqlerrm); ??????????? ??

33.? ???if?cur_policy%isopen?then??? ??

34.? ??????close?cur_policy; ??

35.? ???end?if; ??

36.? end; ??

37.? /??

Set serveroutput on;

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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 ('2','3','4')

??? ?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

???? when others then

???????? close cur_policy;

???????? Dbms_Output.put_line(Sqlerrm);

??? ?????

?? if cur_policy%isopen then??

????? close cur_policy;

?? end if;

end;

/

3）

Sql代碼

1.?? Set?serveroutput?on; ??

2.?? ??

3.?? declare? ??

4.?? ????Cursor?cur_policy?is??

5.?? ?????select?cm.policy_code,?cm.applicant_id,?cm.period_prem,cm.bank_code,cm.bank_account ??

6.?? ?????from?t_contract_master?cm ??

7.?? ?????where?cm.liability_state?=?2 ??

8.?? ?????and?cm.policy_type?=?1 ??

9.?? ?????and?cm.policy_cate?in?('2','3','4') ??

10.? ?????and?rownum?<?5 ??

11.? ?????order?by?cm.policy_code?desc; ??

12.? Begin??

13.? ???For?rec_Policy?in?cur_policy?loop ??

14.? ???????Dbms_Output.put_line(rec_policy.policy_code); ??

15.? ???end?loop; ??

16.? ???Exception? ??

17.? ?????when?others?then??

18.? ?????????Dbms_Output.put_line(Sqlerrm); ????????? ??

19.? end; ??

20.? ??

21.? /??

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 ('2','3','4')

???? 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;

?

/

run pl/sql,執行結果如下：

Sql代碼

1.?? SQL>? ??? ??

2.?? 8780203932 ??

3.?? 8780203227 ??

4.?? 8780203218 ??

5.?? 8771289268 ??? ??

6.? PL/SQL?procedure?successfully?completed??

SQL>

?

8780203932

8780203227

8780203218

8771289268

?

PL/SQL procedure successfully completed

3． Ref Cursor（動態游標）：
1） 與隱式Cursor,顯式Cursor的區別：

Ref Cursor是可以通過在運行期間傳遞參數來獲取數據結果集。而另外兩種Cursor，是靜態的，在編譯期間就決定數據結果集。
2） Ref cursor的使用:
? ?Type [Cursor type name] is ref cursorü
? ?Define 動態的Sql語句ü
?? Open cursorü
?? 操作數據---Fetch? [Cursor name]ü
?? Close Cursorü
下面是一個Sample：

Sql代碼

1.?? Set?serveroutput?on; ??

2.?? ??

3.?? Declare??

4.?? ????---define?cursor?type?name ??

5.?? ????type?cur_type?is?ref?cursor; ??

6.?? ????cur_policy?cur_type; ??

7.?? ????sqlStr?varchar2(500); ??

8.?? ????rec_policy?t_contract_master%rowtype; ??

9.?? begin??

10.? ???---define?動態Sql ??

11.? ???sqlStr?:=?'select?cm.policy_code,?cm.applicant_id,?cm.period_prem,cm.bank_code,cm.bank_account?from?t_contract_master?cm ??

12.? ?????where?cm.liability_state?=?2? ??

13.? ?????and?cm.policy_type?=?1? ??

14.? ?????and?cm.policy_cate?in?(2,3,4)? ??

15.? ?????and?rownum?<?5? ??

16.? ?????order?by?cm.policy_code?desc?'; ??

17.? ---Open?Cursor ??

18.? ??open?cur_policy?for?sqlStr; ??

19.? ??loop ??

20.? ???????fetch?cur_policy?into?rec_policy.policy_code,?rec_policy.applicant_id,?rec_policy.period_prem,rec_policy.bank_code,rec_policy.bank_account; ??

21.? ???????exit?when?cur_policy%notfound; ???????? ??

22.? ???????Dbms_Output.put_line('Policy_code:'||rec_policy.policy_code); ??? ??

23.? ??end?loop; ??

24.? close?cur_policy;?????

25.? end; ??

26.? /??Set serveroutput on;

?

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 動態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;

/

4.常見Exception

Sql代碼

1.?? 錯?誤?名?稱?錯誤代碼????錯?誤?含?義??? ??

2.?? CURSOR_ALREADY_OPEN?ORA_06511???試圖打開已經打開的游標??? ??

3.?? INVALID_CURSOR??ORA_01001???試圖使用沒有打開的游標??? ??

4.?? DUP_VAL_ON_INDEX????ORA_00001???保存重復值到惟一索引約束的列中??? ??

5.?? ZERO_DIVIDE?ORA_01476???發生除數為零的除法錯誤??? ??

6.?? INVALID_NUMBER??ORA_01722???試圖對無效字符進行數值轉換??? ??

7.?? ROWTYPE_MISMATCH????ORA_06504???主變量和游標的類型不兼容??? ??

8.?? VALUE_ERROR?ORA_06502???轉換、截斷或算術運算發生錯誤??? ??

9.?? TOO_MANY_ROWS???ORA_01422???SELECT…INTO…語句返回多于一行的數據??? ??

10.? NO_DATA_FOUND???ORA_01403???SELECT…INTO…語句沒有數據返回??? ??

11.? TIMEOUT_ON_RESOURCE?ORA_00051???等待資源時發生超時錯誤??? ??

12.? TRANSACTION_BACKED_OUT??ORA_00060???由于死鎖，提交失敗??? ??

13.? STORAGE_ERROR???ORA_06500???發生內存錯誤??? ??

14.? PROGRAM_ERROR???ORA_06501???發生PL/SQL內部錯誤??? ??

15.? NOT_LOGGED_ON???ORA_01012???試圖操作未連接的數據庫??? ??

16. LOGIN_DENIED????ORA_01017???在連接時提供了無效用戶名或口令

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?是從這篇文章轉載的：http://www.javaeye.com/topic/649874

轉載于:https://www.cnblogs.com/emmy/archive/2011/01/10/1931699.html

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