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CSE 103

CSE 103. Review Day 07 in the book What are entities ? How are they stored? What are records ? How are they stored? What are attributes ? How are they stored? What is a 1:N relationship ? M:N relationship ? 1:1 relationship ? What is a foreign key ?

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CSE 103

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  1. CSE 103 • Review Day 07 in the book • What are entities? How are they stored? • What are records? How are they stored? • What are attributes? How are they stored? • What is a 1:N relationship? • M:N relationship? • 1:1 relationship? • What is a foreign key? • Continue to Day 08 in the text, if you finish http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  2. Debrief Homework • Import data from the text file CanadianUniversities06.txt into a temporary table. • Construct an APPEND query to copy select data from this table into the appropriate fields in table tbl_Schools http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  3. Relational Databases • From the Day 7 reading: • What are entities? How are they stored? • What are records? How are they stored? • What are attributes? How are they stored? • What is a 1:N relationship? • M:N relationship? • 1:1 relationship? • What is a foreign key? http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  4. Relationships in the music_linked_07 database • Copy the music_linked_07database and open it in Access • Similar but not identical to musicdemo • Identify relationships between the tables • Classify each as M:N, 1:N, or 1:1 • How did you find there was a relationship of any kind? • How did you know what type it was? • How is each type implemented in the database? http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  5. Database Design • Using tables and relations between the tables allows us to store information with a minimum of redundancy • How do we extract information from a multi-table database? • How do multi-table queries incorporate the relations between the tables? • e.g., Which albums were released on the Sony label? http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  6. Questions about JOINS • The JOIN operation is discussed on 8-2 and 8-3 of the textbook. • What are the three steps in the JOIN operation called? • What is meant by each of these terms? http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  7. Pencil and Paper JOIN Exercise • Worksheet with two partial tables • tbl_Movies and tbl_MovieGenres • The JOIN table is partially complete • First operation is unfinished • Complete all steps of the JOIN operation • Which rows are left in the final JOIN table? How many columns are there? http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  8. Constructing a Multi-Table Query in SQL • First operation: PRODUCT SELECT tbl_Movies.MovieID, MovieTitle, Year, tbl_MovieGenres.MovieID, GenreType, RankFROM tbl_Movies, tbl_MovieGenresWHERE (tbl_Movies.MovieID = 176658 OR tbl_Movies.MovieID = 331381 OR tbl_Movies.MovieID = 348396) AND (tbl_MovieGenres.MovieID = 176658 OR tbl_MovieGenres.MovieID = 331381 OR tbl_MovieGenres.MovieID = 348396) http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  9. Query Construction, cont. • What condition should we enforce to get only those records from the two tables that match on the common attribute?(SELECT) • How many rows are returned now? • How can we remove the duplicate column? (PROJECT) • How else can we write the FROM line? http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  10. Multiple-table queries:SQL INNER JOIN … ON • FROM t1, t2 takes full product of two tables: every row in t1 matched with every row in t2 • Have to restrict WHERE clause usually • FROM t1 INNER JOIN t2 ON t1.col1 = t2.col2 takes INNER JOIN of two tables: only rows meeting the ON condition returned • Second syntax is preferred • We can leave the WHERE clause for actual restrictions on the data • The FROM line will cover relationships http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  11. Multiple Table Queries in SQL • Construct the following queries • list the Movie Titles and Years in which Actor 90715 appeared [48] • How could we start with the Actor name instead? • list the Movie Titles and Years that Director 379723 made [61] • How could we start with the Director name? • Find the movieIDs for all the movies that have Klingon as a language [13] • How could we then find these MovieTitles? http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

  12. Homework • Check the link on the today page for homework to do before Day 8 • Reread Days 7 and 8 to understand relationships and INNER JOINs • Read Day 11 to learn about OUTER JOINS - how they differ from INNER and their use • Also read about "self" JOINs and understand their use • Practice problems using INNER JOIN are available http://www.cse.msu.edu/~cse103 U:/msu/course/cse/103

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