SQL

Some useful bits and pieces I've come across for using SQL, mostly the Teradata variant.

Jamie Whitehorn
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Using Teradata SQL: Finding a person's age

How to calculate a person's age correctly given a date and their date of birth in Teradata SQL.

Jamie Whitehorn
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Using Teradata SQL: Check the size of tables in a database

Some useful SQL that lets you find how much disk space your database and tables are actually using.

Jamie Whitehorn
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Using Teradata SQL: Create a reference table for human generations

Useful SQL to create a reference table of human generations like Millennial, Generation X, Baby Boomer etc with start and end dates.

Jamie Whitehorn
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Using Teradata SQL: How to find all the tables in a database or user area

This SQL lets you find all the tables in a particular database or your user area (your personal database) in Teradata, or table names that match a pattern.

Jamie Whitehorn
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Using Teradata SQL: Find the difference between two timestamps and express as hours

How to compare two timestamps in SQL and express the result in hours.

Jamie Whitehorn
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Using Teradata SQL: How to find the number of AMPs and Nodes

How to find the number of AMPs and Nodes in a Teradata installation using a simple SQL query.

Jamie Whitehorn
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Using Teradata SQL: How to drop (aka delete) a lot of tables at once

This SQL creates a series of commands that can be used to DROP (aka delete) all the TABLES that match a pattern or username.

Jamie Whitehorn
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Using Teradata SQL: How to check if a table exists

Explains how to use SQL to check if a table already exists. Very useful to check prior to dropping a table, or for volatile tables if you re-run SQL.

Jamie Whitehorn
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Using Teradata SQL: Validating a UK Postcode

This one came about because a set of data I was dealing with had UK postcodes in it. The data came in from a whole variety of sources, and as such, was not very good in quality terms. The system that the data was going to, on the other hand

Jamie Whitehorn
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Using Teradata SQL: Create a table from another table or select statement

OK, this one is fairly basic for anyone who regularly uses SQL, but it's a neat trick if you're not familiar with it. Normally when you create a table you have to specify all the fields and their formats in the CREATE statement. Then you populate it with an INSERT

Jamie Whitehorn
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Using Teradata SQL: How to find the first or last record in a sequence

If your reading a lot of records from a database and you need to find the first or last record in a sequence, you can do this in MS SQL by using TOP 1, or in MySQL by using LIMIT 1. QUALIFY OVER PARTITION But TOP and LIMIT don't exist