Introduction to Data Management CSE 344. Section 6: Relational Calculus and Some XML

Transcription

1 Introduction to Data Management CSE 344 Section 6: Relational Calculus and Some XML CSE Fall

2 Relational Calculus Review Relational predicate P is a formula given by this grammar: P ::= atom P P P P P P not(p) x.p x.p Query Q: Q(x1,, xk) = P CSE Fall

3 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. CSE Fall

4 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. Q(x) = y. z. Frequents(x, y) Serves(y,z) Likes(x,z) CSE Fall

5 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. Q(x) = y. z. Frequents(x, y) Serves(y,z) Likes(x,z) Find drinkers that frequent only bars that serves some beer they like. CSE Fall

6 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. Q(x) = y. z. Frequents(x, y) Serves(y,z) Likes(x,z) Find drinkers that frequent only bars that serves some beer they like. Q(x) = y. Frequents(x, y) ( z. Serves(y,z) Likes(x,z)) CSE Fall

7 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. Q(x) = y. z. Frequents(x, y) Serves(y,z) Likes(x,z) Find drinkers that frequent only bars that serves some beer they like. Q(x) = y. Frequents(x, y) ( z. Serves(y,z) Likes(x,z)) Find drinkers that frequent some bar that serves only beers they like. CSE Fall

8 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. Q(x) = y. z. Frequents(x, y) Serves(y,z) Likes(x,z) Find drinkers that frequent only bars that serves some beer they like. Q(x) = y. Frequents(x, y) ( z. Serves(y,z) Likes(x,z)) Find drinkers that frequent some bar that serves only beers they like. Q(x) = y. Frequents(x, y) z.(serves(y,z) Likes(x,z)) CSE Fall

9 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. Q(x) = y. z. Frequents(x, y) Serves(y,z) Likes(x,z) Find drinkers that frequent only bars that serves some beer they like. Q(x) = y. Frequents(x, y) ( z. Serves(y,z) Likes(x,z)) Find drinkers that frequent some bar that serves only beers they like. Q(x) = y. Frequents(x, y) z.(serves(y,z) Likes(x,z)) Find drinkers that frequent only bars that serves only beer they like. CSE Fall

10 Likes(drinker, beer) Frequents(drinker, bar) Serves(bar, beer) Review Examples Find drinkers that frequent some bar that serves some beer they like. Q(x) = y. z. Frequents(x, y) Serves(y,z) Likes(x,z) Find drinkers that frequent only bars that serves some beer they like. Q(x) = y. Frequents(x, y) ( z. Serves(y,z) Likes(x,z)) Find drinkers that frequent some bar that serves only beers they like. Q(x) = y. Frequents(x, y) z.(serves(y,z) Likes(x,z)) Find drinkers that frequent only bars that serves only beer they like. Q(x) = y. Frequents(x, y) z.(serves(y,z) Likes(x,z)) CSE Fall

11 Uses(recipe, ingredient_name) Ingredient(name, category) Exercises We have a database of recipes and ingredients. An ingredient has a name and a category (meat, dairy, veggie, etc.). The relation uses captures which recipe uses which ingredient. Write a relational calculus query that returns all recipes that use ingredients from at least two different categories. Q(r) = i1. i2. c1. c2. Uses(r, i1) Uses(r,i2) Ingredient(i1,c1) Ingredient(i2,c2) c1!= c2 CSE Fall

12 Uses(recipe, ingredient_name) Ingredient(name, category) Exercises We have a database of recipes and ingredients. An ingredient has a name and a category (meat, dairy, veggie, etc.). The relation uses captures which recipe uses which ingredient. Write a relational calculus query that returns all recipes that use only one category of ingredients. Return the recipe and the category. Q(r,c) = i. n. Uses(r,i) Ingredient(n,c) i2.(uses(r,i2) Ingredient(i2,c)) CSE Fall

13 Uses(recipe, ingredient_name) Ingredient(name, category) Exercises We have a database of recipes and ingredients. An ingredient has a name and a category (meat, dairy, veggie, etc.). The relation uses captures which recipe uses which ingredient. Write a relational calculus query that returns all ingredients that are never used in a recipe. Q(i) = c. Ingredient(i,c) not( r. Uses(r,i)) CSE Fall

14 Uses(recipe, ingredient_name) Ingredient(name, category) Exercises We have a database of recipes and ingredients. An ingredient has a name and a category (meat, dairy, veggie, etc.). The relation uses captures which recipe uses which ingredient. Write a relational calculus query that returns pairs of recipes that use the same categories of ingredients but never dairy. Q(r1,r2) = i1. i2. c. (c!= Dairy ) Uses(r1,i1) Uses(r2,i2) i3. (Uses(r1,i3) i4. (Uses(r2,i4) Ingredient(i3,c) Ingredient(i4,c)) i5. (Uses(r2,i5) i6. (Uses(r1,i6) Ingredient(i5,c) Ingredient(i6,c))) CSE Fall

15 XML CSE Fall

16 Saxon Setup Download Saxon Download Mondial dataset and DTD Make sure Java VM is installed

17 Practice with Saxon Open text editor and save a query: <result> </result> { Xpath expression} Run the program $ java -cp saxon9he.jar net.sf.saxon.query ex.xq > a1.xml To pretty print $ xmllint --format a1.xml