labelling distinct elements of a column - mysql

Question

Below is the table of animals on various floors.
ID,FLOOR_LEVEL,ANIMAL [column names]
01,A,CAT
02,A,DOG
03,B,DOG
04,B,CAT
05,B,CAT
06,C,CAT
I want to label the types of animal(i.e cat will be labelled as 1, dog will be labelled as 2....) like shown below by creating a new column LABEL.
ID,FLOOR_LEVEL,ANIMAL,LABEL [column names]
01,A,CAT,1
02,A,DOG,2
03,B,DOG,2
04,B,CAT,1
05,B,CAT,1
06,C,CAT,1
It can be done by writing query such as
INSERT INTO table_name (LABEL)
VALUES (1,2,2,1,1,1);
But, how can this be generalised for a huge no. of different type of animals in MySQL by writing query? Please help.

Answer 1

Your INSERT statement makes no sense:
INSERT INTO table_name (LABEL) VALUES (1,2,2,1,1,1);
Will insert 1 row into a table called table_name with 6 columns. It would do nothing for you.
Instead make a new table to store the animal id and animal name:
CREATE TABLE animals ( id int, animal_name VARCHAR(50));
INSERT INTO animals VALUES (1, 'cat'),(2, 'dog'),(3,'tardigrade'),(4,'liger');
And then join that into your query:
SELECT t1.floor_level, t1.animal, t2.id
FROM table t1
INNER JOIN animals t2 ON
t1.animal = t2.animal_name;
Optionally you could use a case statement to do this within the query. It will get a little laborious if you have a ton of animals though. And you will have to rewrite it every time you query this table.
SELECT floor_level,
animal,
CASE WHEN animal = 'cat' THEN 1
WHEN animal = 'dog' THEN 2
WHEN animal = 'tardigrade' THEN 3
WHEN animal = 'liger' THEN 4
END as animal_id
FROM table;

Answer 2

If your requirement is not a numeric label, try using md5() to generate a hash label for the animals. Its value would be same for animals with same name (case sensitive).
SELECT ID, FLOOR_LEVEL, ANIMAL, MD5(UPPER(ANIMAL))
FROM table;
Please note that MD5() string are case sensitive. i.e. DOG and Dog would generate a different output, hence I have used UPPER() method.
Another option is to use below function, which will convert the alphanumeric md5() value to a long type. But the numeric value would not be starting from 1, 2 etc.
cast(conv(substring(md5(upper(animal)), 1, 16), 16, 10) as unsigned integer)
EDIT - Based on OP comment
But is there any way to reduce the length of generated values?
To reduce the length of the generated value, Use rand() function wisely to reduce the length of the integer. The only concern is that you may not want a collision of generated values.
round(cast(conv(substring(md5(upper(animal)), 1, 16), 16, 10) as unsigned integer) * (rand() * rand()))
A more sophisticated, optimized and non-colliding value may be generated using Hive UDF.

Answer 3

The simplest way to solve your problem is with a DECODE
SELECT
DECODE(
ANIMAL,
'CAT',1,
'DOG',2,
'OTHER'
)
FROM ...
Here is more info:
https://docs.oracle.com/cd/B19306_01/server.102/b14200/functions040.htm
Good Luck!

Answer 4

The command you are looking for is CASE
SELECT ID, FLOOR_LEVEL, ANIMAL,
CASE
WHEN ANIMAL = 'CAT' THEN 1
WHEN ANIMAL = 'DOG' THEN 2
END
FROM table;