[毎日1題]OCP 1 z 0-047:2013-08-28  DELETE..........................................................160

転載は出典を明記してください.http://blog.csdn.net/guoyjoe/article/details/10475707
ACDは問題ライブラリに基づいて、操作は以下の通りです:A答えは削除できます:

oe@OCM> delete from order_items   2  WHERE order_id IN (SELECT order_id FROM orders   3  WHERE order_status IN(0,1));  110 rows deleted.  oe@OCM> rollback;  Rollback complete. 

B答えは削除できません:このような文法はありません(DELETE*FROM、つまりDELETEの後で直接表名に付いて、*を使うことができません)

oe@OCM> DELETE *    2  FROM order_items   3  WHERE order_id IN(SELECT order_id   4  FROM orders   5  WHERE orders   6  WHERE order_status IN(0,1)); DELETE *        * ERROR at line 1: ORA-00903: invalid table name 

C答えは削除できます.

oe@OCM> delete from order_items i   2  WHERE order_id=(SELECT order_id FROM orders o   3  WHERE i.order_id=o.order_id AND   4  order_status IN(0,1));  110 rows deleted.  oe@OCM> rollback;  Rollback complete.

D答えも削除できます.

oe@OCM> delete from(select * from order_items i,orders o   2  WHERE i.order_id=o.order_id AND order_status in(0,1));   110 rows deleted. 

Dが削除できる原因を分析する:
1、ORDERS表に主キーがあるORDER_ID:CONSTRAINT "ORDER_PK"PRIMARY KEY ("ORDER_ID").
次の赤いフォントを見てください.
　

oe@OCM> select dbms_metadata.get_ddl('TABLE','ORDERS') from dual;  DBMS_METADATA.GET_DDL('TABLE','ORDERS') --------------------------------------------------------------------------------    CREATE TABLE "OE"."ORDERS"    (    "ORDER_ID" NUMBER(12,0),         "ORDER_DATE" TIMESTAMP (6) WITH LOCAL TIME ZONE CONSTRAINT "ORDER_DATE_NN" NOT NULL ENABLE,         "ORDER_MODE" VARCHAR2(8),         "CUSTOMER_ID" NUMBER(6,0) CONSTRAINT "ORDER_CUSTOMER_ID_NN" NOT NULL ENABLE,         "ORDER_STATUS" NUMBER(2,0),         "ORDER_TOTAL" NUMBER(8,2),         "SALES_REP_ID" NUMBER(6,0),         "PROMOTION_ID" NUMBER(6,0),          CONSTRAINT "ORDER_MODE_LOV" CHECK (order_mode in ('direct','online')) ENABLE,          CONSTRAINT "ORDER_TOTAL_MIN" CHECK (order_total >= 0) ENABLE,          CONSTRAINT "ORDER_PK" PRIMARY KEY ("ORDER_ID")   USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS NOLOGGING   STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645   PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1   BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)   TABLESPACE "EXAMPLE"  ENABLE,          CONSTRAINT "ORDERS_SALES_REP_FK" FOREIGN KEY ("SALES_REP_ID")           REFERENCES "HR"."EMPLOYEES" ("EMPLOYEE_ID") ON DELETE SET NULL ENABLE,          CONSTRAINT "ORDERS_CUSTOMER_ID_FK" FOREIGN KEY ("CUSTOMER_ID")           REFERENCES "OE"."CUSTOMERS" ("CUSTOMER_ID") ON DELETE SET NULL ENABLE    ) SEGMENT CREATION IMMEDIATE   PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255  NOCOMPRESS NOLOGGING   STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645   PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1   BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)   TABLESPACE "EXAMPLE" 

2、ORDER_TIEMSテーブルに外部キーORDER_がありますID:CONSTRAINT "ORDER_ITEMS_ORDER_ID_FK"FOREIGN KEY ("ORDER_ID")
          REFERENCES"OE"."ORDERS"("ORDER_ID")ON DELETE CASCADE ENABLE NOVALLIDATE、メイン外部キーを付けてカスケード削除できます.
次の赤いフォントを見てください.

oe@OCM> select dbms_metadata.get_ddl('TABLE','ORDER_ITEMS') from dual;  DBMS_METADATA.GET_DDL('TABLE','ORDER_ITEMS') --------------------------------------------------------------------------------    CREATE TABLE "OE"."ORDER_ITEMS"    (    "ORDER_ID" NUMBER(12,0),         "LINE_ITEM_ID" NUMBER(3,0) NOT NULL ENABLE,         "PRODUCT_ID" NUMBER(6,0) NOT NULL ENABLE,         "UNIT_PRICE" NUMBER(8,2),         "QUANTITY" NUMBER(8,0),          CONSTRAINT "ORDER_ITEMS_PK" PRIMARY KEY ("ORDER_ID", "LINE_ITEM_ID")   USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS NOLOGGING   STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645   PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1   BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)   TABLESPACE "EXAMPLE"  ENABLE,          CONSTRAINT "ORDER_ITEMS_ORDER_ID_FK" FOREIGN KEY ("ORDER_ID")           REFERENCES "OE"."ORDERS" ("ORDER_ID") ON DELETE CASCADE ENABLE NOVALIDATE,          CONSTRAINT "ORDER_ITEMS_PRODUCT_ID_FK" FOREIGN KEY ("PRODUCT_ID")           REFERENCES "OE"."PRODUCT_INFORMATION" ("PRODUCT_ID") ENABLE    ) SEGMENT CREATION IMMEDIATE   PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255  NOCOMPRESS NOLOGGING   STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645   PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1   BUFFER_POOL DEFAULT FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)   TABLESPACE "EXAMPLE" 

         サブテーブルのレコードが削除されました:
　　

oe@OCM> select count(*) from orders;　　　　－－      COUNT(*) ----------        105  oe@OCM> select count(*) from order_items;　　－－      COUNT(*) ----------        665  oe@OCM> delete from(select * from order_items i,orders o   2     WHERE i.order_id=o.order_id AND order_status in(0,1));  110 rows deleted.  oe@OCM> select count(*) from orders;　　　－－        COUNT(*) ----------        105  oe@OCM> select count(*) from order_items;　　－－    110     COUNT(*) ----------        555 

          この操作をシミュレートするとき、ずっと間違っている(ERROR at line 1:
ORA-01752:cannot delete from view without exactly one key-preserved table)理由は、自分が2つのテーブルorderとorderを作ったからです.itemsの場合、両テーブルに制約プライマリ外部キーは作成されず、プライマリ外部キーを追加してカスケード削除することができる(CONTRAINT「ORDER_ITEMS_ORDER_ID_FK」FOREGN KEY(「ORDER_ID」)REFERENCES「OE」.「ORDERS」(「ORDER_ID」)ON DELETE CASCADE ENABLE NOVALLIDATE).
これはもうテストしません.簡単すぎます.
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