Determining the default database charset and collation in MySQL - mysql

Question

In MySQL, what is the best way of programmatically retrieving the character set and the collation of the current database?
Is the following:
SELECT
default_character_set_name, default_collation_name
FROM
information_schema.SCHEMATA
WHERE
SCHEMA_NAME = SCHEMA()
identical to the below example?
select ##character_set_database, ##collation_database

Answer 1

According to the documentation:
character_set_database
...
The character set used by the default
database. The server sets this variable whenever the default database
changes. If there is no default database, the variable has the same
value as character_set_server.
...
and
collation_database
...
The collation used by the default database. The
server sets this variable whenever the default database changes. If
there is no default database, the variable has the same value as
collation_server.
...
with both sentences would obtain the same result:
SELECT
default_character_set_name, default_collation_name
FROM
information_schema.SCHEMATA
WHERE
SCHEMA_NAME = SCHEMA()
and
select ##character_set_database, ##collation_database
demonstrated in the following test:
mysql> DROP DATABASE IF EXISTS `my_database`;
Query OK, 0 rows affected (0.01 sec)
mysql> SELECT SCHEMA();
+----------+
| SCHEMA() |
+----------+
| NULL |
+----------+
1 row in set (0.00 sec)
mysql> SELECT
-> ##SESSION.character_set_database,
-> ##SESSION.collation_database,
-> ##SESSION.character_set_server,
-> ##SESSION.collation_server;
+----------------------------------+------------------------------+--------------------------------+----------------------------+
| ##SESSION.character_set_database | ##SESSION.collation_database | ##SESSION.character_set_server | ##SESSION.collation_server |
+----------------------------------+------------------------------+--------------------------------+----------------------------+
| latin1 | latin1_swedish_ci | latin1 | latin1_swedish_ci |
+----------------------------------+------------------------------+--------------------------------+----------------------------+
1 row in set (0.00 sec)
mysql> CREATE DATABASE IF NOT EXISTS `my_database`
-> CHARACTER SET utf8mb4
-> COLLATE utf8mb4_general_ci;
Query OK, 1 row affected (0.00 sec)
mysql> SELECT SCHEMA();
+----------+
| SCHEMA() |
+----------+
| NULL |
+----------+
1 row in set (0.00 sec)
mysql> SELECT
-> ##SESSION.character_set_database,
-> ##SESSION.collation_database,
-> ##SESSION.character_set_server,
-> ##SESSION.collation_server;
+----------------------------------+------------------------------+--------------------------------+----------------------------+
| ##SESSION.character_set_database | ##SESSION.collation_database | ##SESSION.character_set_server | ##SESSION.collation_server |
+----------------------------------+------------------------------+--------------------------------+----------------------------+
| latin1 | latin1_swedish_ci | latin1 | latin1_swedish_ci |
+----------------------------------+------------------------------+--------------------------------+----------------------------+
1 row in set (0.00 sec)
mysql> USE `my_database`;
Database changed
mysql> SELECT SCHEMA();
+-------------+
| SCHEMA() |
+-------------+
| my_database |
+-------------+
1 row in set (0.00 sec)
mysql> SELECT
-> ##SESSION.character_set_database,
-> ##SESSION.collation_database,
-> ##SESSION.character_set_server,
-> ##SESSION.collation_server;
+----------------------------------+------------------------------+--------------------------------+----------------------------+
| ##SESSION.character_set_database | ##SESSION.collation_database | ##SESSION.character_set_server | ##SESSION.collation_server |
+----------------------------------+------------------------------+--------------------------------+----------------------------+
| utf8mb4 | utf8mb4_general_ci | latin1 | latin1_swedish_ci |
+----------------------------------+------------------------------+--------------------------------+----------------------------+
1 row in set (0.00 sec)
mysql> SELECT
-> `DEFAULT_CHARACTER_SET_NAME`,
-> `DEFAULT_COLLATION_NAME`
-> FROM
-> `information_schema`.`SCHEMATA`
-> WHERE
-> SCHEMA_NAME = SCHEMA();
+----------------------------+------------------------+
| DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME |
+----------------------------+------------------------+
| utf8mb4 | utf8mb4_general_ci |
+----------------------------+------------------------+
1 row in set (0.00 sec)
however, a union of both sentences would not be wrong:
mysql> USE `my_database`;
Database changed
mysql> SELECT
-> `DEFAULT_CHARACTER_SET_NAME`,
-> `DEFAULT_COLLATION_NAME`
-> FROM
-> `information_schema`.`SCHEMATA`
-> WHERE
-> SCHEMA_NAME = SCHEMA() AND
-> `DEFAULT_CHARACTER_SET_NAME` = ##SESSION.character_set_database AND
-> `DEFAULT_COLLATION_NAME` = ##SESSION.collation_database;
+----------------------------+------------------------+
| DEFAULT_CHARACTER_SET_NAME | DEFAULT_COLLATION_NAME |
+----------------------------+------------------------+
| utf8mb4 | utf8mb4_general_ci |
+----------------------------+------------------------+
1 row in set (0.00 sec)