SQL joins and Venn diagrams

Posted on July 5, 2016. Filed under: Uncategorized | Tags: , , , |

Here’s a couple of articles on using Venn diagrams to explain SQL joins. For… A Visual Explanation of SQL Joins – Jeff Atwood (coding horror) Since SQL joins appear to be set-based, the use of Venn diagrams to explain them seems, at first blush, to be a natural fit. However, I found that Venn diagrams […]

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Comparison of different SQL implementations

Posted on September 22, 2015. Filed under: Uncategorized | Tags: , , , , , , , , |

Comparison of different SQL implementations The goal of this page — which is a work in progress — is to gather information relevant for people who are porting SQL from one product to another and/or are interested in possibilities and limits of ‘cross-product’ SQL.

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What is a NoSQL Database? Learn By Writing One In Python

Posted on September 2, 2014. Filed under: Uncategorized | Tags: , , , , , , , |

What is a NoSQL Database? Learn By Writing One In Python NoSQL is a term that has become ubiquitous in recent years. But what does “NoSQL” actually mean? How and why is it useful? In this article, we’ll answer these questions by creating a toy NoSQL database in pure Python (or, as I like to […]

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Database design with UML and SQL

Posted on May 14, 2012. Filed under: Uncategorized | Tags: , , , |

www.tomjewett.com/dbdesign/

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Using SQLite triggers to increment a count

Posted on October 6, 2011. Filed under: Uncategorized | Tags: , , , |

I want to apply tags to urls and keep a count of how many times each tag has been used. Here’s some code that does just that: use DBI; use Text::Table; my $FILENAME = ‘play.sqlite’; unlink $FILENAME; my $dsn = “dbi:SQLite:database=$FILENAME”; my $dbh = DBI->connect($dsn) or die; $dbh->do($_) or die “$DBI::errstr for $_” for split […]

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