Flashcards · 2210 · Topic 9

Databases flashcards

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What is a single-table (flat-file) database?: A database in which all the data is held in one table of records and fields.
Fields run down or across a table, and what about records?: Fields are the columns, each holding one kind of data. Records are the rows, each holding all the data about one item.
How do you rule out a field as the primary key?: Look for repeated values in the data. A field such as a surname, where two records share a value, cannot identify one record on its own.
Which data types would you choose for WeightKg, Vaccinated, Species and Visits?: WeightKg: real. Vaccinated: Boolean. Species: text. Visits: integer.
Write SQL to list PetName and OwnerSurname of every dog in table Pet: SELECT PetName, OwnerSurname FROM Pet WHERE Species = 'Dog';
How do you list results with the largest value first in SQL?: Add ORDER BY the field followed by DESC. ORDER BY sorts in ascending order unless DESC is added.
What do SUM and COUNT return in an SQL query?: SUM returns the total of the values in a numeric field for the selected records. COUNT returns the number of records that meet the WHERE condition.
When are quotation marks needed in an SQL condition?: Around a text value, e.g. Species = 'Dog'. Numbers are written without quotation marks, e.g. WeightKg > 20.