How to use a user variable in 'USE database' statement - mysql

Question

I want to make the name of my MYSQL database variable, so it can be set from the outside (a python script) to whatever I like. Thus avoiding hardcoding the name of the database.
I tried passing the name via defining a user variable in the mysql client and then loading the sql script. I was able to create the database but not to connect to it via the USE statement
Definition of variable and calling the sql script:
mysql> SET #database_name = 'name';
mysql> SOURCE script.sql;
Code of script.sql:
-- creating database according to user variable
SET #query = CONCAT('CREATE SCHEMA IF NOT EXISTS ', #database_name, ' DEFAULT CHARACTER SET latin1');
PREPARE stmt FROM #query; EXECUTE stmt; DEALLOCATE PREPARE stmt;
-- selecting the database according to the user variable
SET #query = CONCAT('USE ', #database_name);
PREPARE stmt FROM #query; EXECUTE stmt; DEALLOCATE PREPARE stmt;
I expected that this would work, but unexpectedly MYSQL threw this error into my face:
This command is not supported in the prepared statement protocol yet
The problem is, that there are a lot of table defintions in this script, and they all need the actual database name in front of them, or the USE statement has to work, so the correct database is selected and no database name is needed when creating the tables.
I am grateful for any useful tips, thank you :).

Answer 1

A "complex" workaround might be to generate a .sql file if you have FILE privilege and the secure_file_priv system variable is set also max_allowed_packet also might to be changed.
# SET SESSION max_allowed_packet = '<>'; commented because it might be needed to generate larger .sql file
SET SESSION group_concat_max_len = ##max_allowed_packet;
SELECT
GROUP_CONCAT(sql_lines.line SEPARATOR ';');
FROM (
SELECT CONCAT('CREATE SCHEMA IF NOT EXISTS ', #database_name, 'DEFAULT CHARACTER SET latin1') AS line
UNION
SELECT CONCAT('USE ', #database_name) AS line
) AS sql_lines
CROSS JOIN (
SELECT #database_name = '<test>'
) AS init_user_param
INTO
DUMPFILE '<absolute_file_path>';
SOURCE script.sql;

Answer 2

There is a way, you can generate the sql like you were typing it on the sql prompt. You could write everything like you are typing it, but using a bash script:
Code like this (filename: generate-database.sh):
#!/bin/bash
mydatabase="mytest";
cat << EOF
create database $mydatabase;
use $mydatabase;
create table test1 (id int);
create table test2 (id int);
EOF
You can even pass the database name as the first parameter if you want to have a database for a different site. Then you would do something like this:
bash generate-database.sh | mysql -u <username> -p
Then that will do everything like you would do as if you were typing it in mysql.
To pass in as the first parameter you would do this:
mydatabase=$1;
On the command prompt you would do this:
bash generate-database.sh MarkTownsend | mysql -u <username> -p