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Example: R3 := R1 × R2

R3( A, R1.B, R2.B, C ) ‏ 1 2 5 6 1 2 7 8 1 2 9 10 3 4 5 6 3 4 7 8 3 4 9 10. Example: R3 := R1 × R2. R1( A, B ) ‏ 1 2 3 4 R2( B, C ) ‏ 5 6 7 8 9 10. name. addr. name. manf. Bars. Beers. Sells. Bars sell some beers. license. Drinkers like some beers.

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Example: R3 := R1 × R2

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  1. R3( A, R1.B, R2.B, C )‏ 1 2 5 6 1 2 7 8 1 2 9 10 3 4 5 6 3 4 7 8 3 4 9 10 Example: R3 := R1 × R2 R1( A, B )‏ 1 2 3 4 R2( B, C )‏ 5 6 7 8 9 10

  2. name addr name manf Bars Beers Sells Bars sell some beers. license Drinkers like some beers. Frequents Likes Note: license = beer, full, none Drinkers frequent some bars. Drinkers name addr The schema as an ER-diagram

  3. to output check for Joe check these are equal drinker bar drinker beer tv1 tv2 Sally Bud Sally Joe’s Likes Frequents

  4. Question: Why do we need b1.name < b2.name

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