Using SELECT And UNION ALL To JOIN SQL Tables To CSV Data In MySQL

Using SELECT And UNION ALL To JOIN SQL Tables To CSV Data In MySQL

Ben Nadel merges CSV (Comma-Separated Value) data with a SQL table by generating a derived table via SELECT / UNION ALL statements in MySQL. He then uses the SQL table to augment the existing values in the CSV payload. SQL is so hot right now!

I just love SQL. I've been writing web-applications on top of relational databases (RDBMS) for a while; and, SQL always feels like a luxurious combination of structure and flexibility. Yesterday, when working with some data scientists, I had to merge a few columns from a database table into a CSV (Comma-Separated Values) file that the data scientists had created. The CSV file was fairly small; so, I ended up using the awesome power of multiple-cursors in SublimeText 3 in order to write a SQL query that converted the CSV data into a derived table that I then consumed in an INNER JOIN in MySQL.

To be clear, this is not the only way to consume CSV data in a relational database. But, I was working with a database in which I had read only permissions. As such, I couldn't load the CSV file into a "real table". Given the relatively small size of the CSV payload, what follows just felt like the appropriate level of effort.

That said, let's paint a picture of what was going on. Imagine that I had a database table called friend with the following structure:

SHOW CREATE TABLE friend;
-- Generates the following SQL statement:

CREATE TABLE `friend` (
    `id` int(11) NOT NULL,
    `name` varchar(50) NOT NULL,
    `age` int(11) NOT NULL,
    `catchPhrase` varchar(250) NOT NULL,
    PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8

sql mysql

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