LogiQL and SQL
SQL is a standard language used for defining, manipulating, and querying relational databases. This appendix provides a brief discussion of how basic queries conveyed in SQL may be expressed in LogiQL. Consider the following relational database, which includes two relational tables (Tables H.1...
| Main Authors: | , |
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| Format: | Book Section |
| Language: | English |
| Published: |
Taylor & Francis Group
2015
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| Subjects: | |
| Online Access: | http://eprints.intimal.edu.my/339/ http://eprints.intimal.edu.my/339/1/18_ft.pdf |
| Summary: | SQL is a standard language used for defining, manipulating, and
querying
relational databases. This appendix provides a brief discussion
of how basic queries conveyed in SQL may be expressed in LogiQL.
Consider the following relational database, which includes two relational
tables (Tables H.1 and H.2) describing countries in 2011. The country
table lists the ISO two-letter code, name, and population of various
countries. For discussion purposes, the population of Finland (5,396,292)
is omitted simply to illustrate SQL’s use of a null value to indicate that
a data value is missing (e.g., because it is unknown or inapplicable). To
save space, only a small number of countries are included. For those
countries that have presidents, the president table lists the name, country,
gender, and birth year of those presidents. Australia, Canada, and the
United Kingdom have prime ministers instead of presidents, so they are
not included in the president table.
Throughout the database, countries are standardly identified by their
country codes. The entries in the first two columns of the tables are necessarily
unique, so each of these columns is a candidate key for its table. The
country table has countryCode as its primary key and countryName as an
alternate key. |
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