December 2, 2002 (20:06) from 211.178.25.198 | |
Written by ³ªÁ¹·Á¤Ì.¤Ì; | Hits : 929 , Lines : 54 |
¼±»ý´Ô ´äÁ» ²À! ÇØ ÁÖ¼¼¿ä |
---|
¿ì¼± ¹Ø¿¡ ÀÖ´Â 4Àå Áú¹®Àä. ´äÁ» ÇØ ÁÖ¼¼¿ä. ¸ð¸£°Ú¾î¿ä. 1. Test for Empty Relation ¿¡¼ exists ¾²´Â°Å ³ª¿À°í¿ä ±× ´ÙÀ½¿¡ ¿¹Á¦·Î where not exists ¾²´Â°Å ³ª¿ÀÀÝ¾Æ¿ä ±×°Å ÀÌÇØ°¡ ¾È °¡¿ä. ¼³¸í Á¡ ´Ù½Ã ÇØ ÁÖ¼¼¿ä ±× nested µÈ ºÎºÐÀÌ ¸ðÇϴ°ÇÁö? 2. ±×¸®°í¿ä ¸¸¾à account¸¦ °®°í ÀÖ´Â ¸ðµç °í°´À» À̸§À» Ãâ·ÂÇ϶ó¸é select customer-name from depositor ¶ó°í¸¸ ÇÏ¸é ¾È µÇ°í ¿Ö account¿¡ account-number°¡ ÀÖ´ÂÁö °°ÀÌ È®ÀÎÀ» ÇؾßÇϳª¿ä?? select customer-name from depositor, account where account.account_number=depositer.account_number ÀÌ·¸°Ô ÇÏ´Â°Ô Ã¥¿¡¼´Â ¸Â´Ù´Â°ÅÁÒ? ±×·±µ¥ Depositor relationÀ» ¸¸Á·ÇÏ´Â »ç¶÷ÀÌ¸é ´ç¿¬È÷ account°¡ ÀÖÁö ¾ÊÀ»±î¿ä? 3. ¿ª½Ã 4À弿ä Test for Absence of Duplicate Tuples¿¡¼ Unique³ª¿À´Â ºÎºÐ Áß example query ÀÖÁÒ? °Å±â ù ¿¹Á¦¼ select T.customer-name from depositor as T ¶ó°í ÇÏ°í¼± where unique select R.customer-name from account, depositor as R where T.customer-name=R.customer-name ... À̶ó°í µÇ¾î Àִµ¥ customer nameÀ» ¿Ö 2¹ø °°Àº°É »Ì´ÂÁö ¼³¸í Á» ´Ù½Ã ÇØ ÁÖ¼¼¿ä 5. 4Àå µÞºÎºÐ Embedded SQLµµ °øºÎÇؾßÇϳª¿ä? ²À! ´äÇØÁÖ¼¼¿ä. |