Transitioning to another SQL database? This blog post is for you. Shifting from one SQL dialect to another can be a journey full of surprises. While the basic syntax (SELECT FROM WHERE) is similar, there are important differences, that will make your queries slow, fast, fail or worse: fail silently!

In this blog post I’ll guide you through the intricate pathways of databases I have come across during my work as a data scientist: Postgres, MySQL, SQLite, Hive and Presto (AWS Athena). We’ll start with a brief introduction into the databases and some differences. Then we jump into three pitfalls you have to be aware of.

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table { width:80% !important;} The basic idea of complex datatypes is to store multiple values in a single column. So if you are working with a Hive database and you query a column, but then you notice “This value I need is trapped in a column among other values…” you just came across a complex a.k.a. nested datatype. There are three types: arrays, maps and structs. First, you have to understand, which types are present.

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