Chuong_7_Rang_buoc_toan_ven

Chuong_7_Rang_buoc_toan_ven - Chng 7 RANG BUOC TOAN VEN...

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RAØNG BUOÄC TOAØN VEÏN TREÂN CSDL QUAN HEÄ Chöông 7 NOÄI DUNG I. Ñònh nghóa – Taàm quan troïng cuûa RBTV II. Caùc yeáu toá cuûa RBTV III. Phaân loïai RBTV
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ÑÒNH NGHÓA z RBTV (Integrity Constraints) laø caùc nguyeân taéc maø moïi tình traïng CSDL ñeàu phaûi thoûa. z VD: KQ (MASV, MAMH , DIEM) Ñieåm laø soá thöïc thuoäc [0,10] vaø chính xaùc ñeán 0.5 TAÀM QUAN TRONG CUÛA RBTV z Giuùp CSDL theå hieän trung thöïc theá giôùi thöïc maø CSDL ñang moâ taû. z Ngaên chaën nhöõng thao taùc gaây sai treân CSDL. ) Giuùp CSDL luoân ñuùng ñaén.
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CAÙC YEÁU TOÁ CUÛA RBTV Coù 4 yeáu toá: z Phaùt bieåu: ngoân ngöõ töï nhieân theå hieän ngöõ nghóa cuûa RBTV z Bieåu dieãn: ngoân ngöõ hình thöùc, duøng thuaät toùan (maõ giaû), toùan hoïc, ñaïi soá quan heä, pheùp tính quan heä,. ..ñeå theå hieän z Boái caûnh: Caùc quan heä maø raøng buoäc coù lieân quan z Taàm aûnh höôûng: Caùc thao taùc Theâm, Xoùa, Söûa treân caùc quan heä (laø boái caûnh) coù khaû naêng gaây vi phaïm raøng buoäc hay khoâng (+ coù, -kho âng) PHAÂN LOÏAI RBTV z Boái caûnh RB coù boái caûnh 1 quan heä RB coù boái caûnh nhieàu quan heä z Nguoàn goác
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Chuong_7_Rang_buoc_toan_ven - Chng 7 RANG BUOC TOAN VEN...

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