ORDER BY (the lesser known way)

We all know with MySQL you can use ORDER BY with a list of columns to return an ordered set, e.g. ORDER BY name, type, state;
I often use the syntax ORDER BY 1,2; which I’m surprised that some people do not know about.

However I needed to do some selective ordering of a type field, I didn’t want to for example have a lookup table just to join for ordering. While contemplating a means of achieving this, I asked a work colleague, who I figured may have just experienced this problem before. Lone behold I became the student as I discovered there is a third syntax with ORDER BY, using expressions.

mysql> create table test(name varchar(10) not null, type varchar(10) not null);
Query OK, 0 rows affected (0.06 sec)

mysql> insert into test(name,type) values
('Apples','Fruit'),
('Bananas','Fruit'),
('Carrots','Veg'),
('Onions','Veg'),
('Beer','Liquid'),
('Water','Liquid'),
('Crackers','Food');
Query OK, 7 rows affected (0.00 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> select name from test
order by type='Veg' DESC,
         type='Fruit' DESC,
         type='Food' DESC,
         type='Liquid' DESC;
+----------+
| name     |
+----------+
| Carrots  |
| Onions   |
| Apples   |
| Bananas  |
| Crackers |
| Beer     |
| Water    |
+----------+
7 rows in set (0.00 sec)

Of course, reading the MySQL Manual confirms this on the SELECT command .
I’ve not read the MySQL manual from cover to cover, since 4.x days. Perhaps it’s time.

Thanks to Nick Pisarro of Blog Revolution for this most valuable tip.

Tagged with: Databases MySQL

Producing IQR and Outlier statistics with SQL

The interquartile range (IQR) measures the spread of the middle 50% of a distribution — the distance between the first quartile (Q1) and the third quartile (Q3). Combined with Tukey’s 1.

Producing Mode statistics with SQL

The mode is the value or values that appear most frequently in a dataset. Unlike the mean or median, it applies naturally to categorical and ordinal data — star ratings, product codes, survey responses — and reveals what is most common, not what is average.

Extending MySQL Capabilies with UDFs, Plugins and Components - Part 2

MySQL offers three different approaches to extending the SQL capabilities with the default product you download and install. These are: User Defined Function (UDF) MySQL Manual MySQL Plugin MySQL Manual MySQL Component MySQL Manual In my prior post I provided a new uuidv function that accepted a numeric argument to return a string of the version of UUID specified.