MySQL basic learning database query creation, modification, deletion and use

Query the database:

mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| school |
| sys |
| test |
+--------------------+
6 rows in set (0.03 sec)

The query creation database command and its default character set:

mysql> show create database school;
+----------+--------------------------------------------------------------------
--------------------------------+
| Database | Create Database
|
+----------+--------------------------------------------------------------------
--------------------------------+
| school | CREATE DATABASE `school` /*!40100 DEFAULT CHARACTER SET utf8 */ /*!
80016 DEFAULT ENCRYPTION='N' */ |
+----------+--------------------------------------------------------------------
--------------------------------+
1 row in set (0.00 sec)

Create the database:

mysql> create database data_view;
Query OK, 1 row affected (0.41 sec)

An existing database cannot be created repeatedly, and an error will be reported:

mysql> create database data_view;
ERROR 1007 (HY000): Can't create database 'data_view'; database exists

Using judgment to determine whether there is a database will not report an error:

If you do n’t create it, if you do n’t, you will create it.

mysql> create database if not exists data_view;
Query OK, 1 row affected, 1 warning (0.23 sec)

Specify the character set when creating the database:

For example: gbk

mysql> create database if not exists data_test character set gbk;
Query OK, 1 row affected (0.38 sec)

At this point, check that the character set of the newly created database has become gbk:

mysql> show create database data_test;
+-----------+-------------------------------------------------------------------
-----------------------------------+
| Database | Create Database
|
+-----------+-------------------------------------------------------------------
-----------------------------------+
| data_test | CREATE DATABASE `data_test` /*!40100 DEFAULT CHARACTER SET gbk */
/*!80016 DEFAULT ENCRYPTION='N' */ |
+-----------+-------------------------------------------------------------------
-----------------------------------+
1 row in set (0.00 sec)

Modify the database character set:

mysql> alter database data_test character set utf8;
Query OK, 1 row affected, 1 warning (0.43 sec)

Delete the database (dangerous way):

mysql> drop database if exists data_test;
Query OK, 0 rows affected (0.32 sec)

Check if there is still this database

mysql> show databases;
+--------------------+
| Database |
+--------------------+
| data_view |
| information_schema |
| mysql |
| performance_schema |
| school |
| sys |
| test |
+--------------------+
7 rows in set (0.00 sec)

Use of the database:

Check the current database before using it:

mysql> select database();
+------------+
| database() |
+------------+
| NULL |
+------------+
1 row in set (0.00 sec)

null indicates that the database is not currently used;

Use the database

mysql> use data_view;
Database changed

Check out the currently used database:

mysql> select database();
+------------+
| database() |
+------------+
| data_view |
+------------+
1 row in set (0.00 sec)