SQL-Tutorial

I really like SQL. But sometimes I struggle to undestand some of the concepts. So I write about it. Meanwhile there are a bunch of articles, so time for a overview page: SQL-Basics: Create, Read, Update & Delete SQL-Basics: Relations SQL-Functions – SQL-Basics 3 SQLite3: Python and SQL Subqueries: Update column with values from another…

SQL-LIKE and wildcards

Se_en represents a pattern with a wildcard character. The _ means you can substitute any individual character here without breaking the pattern. The names Seven and Se7en both match this pattern. The percentage sign % is another wildcard character that can be used with LIKE.

SQL-Basics: Relations

As the Junior Data Scientist of Knight Industries we created a table to keep track of all our operatives: SQL-Basics: Create, Read, Update, Delete Devon asks us to keep track of our operations aka missions as well. For the first implementation let us assume that a mission has one operative and an operative can participate…

SQL-Functions – SQL-Basics 3

In SQL-Basics we learned the standard SQL statements to create a table, insert data into it, retrieving data from tables and altering data. Now we want to do even Devon is a data driven man and to evaluate our mission, he likes to know from us: how many missions we finished the total cost of…

SQL-Basics: Create – Read – Update – Delete

This episode is about the basic statements needed to create, read, update and delete data in a database system. Let’s assume we work as a data scientist for Knight Industries.  We want to help the Foundation of Law and Government to keep track of our operatives. We decide to use a classic relational database management…

SQL – the dark side

Sometimes your RDBMS does not allow you to do certain changes like updating a table without using a WHERE clause that uses a key column. When you are really sure what you want to do: SET SQL_SAFE_UPDATES = 0; Now the dirty brown magic can begin! Back to the SQL-Tutorial