Mysql数据库(二)Mysql数据库管理
一 、创建数据库
1.通过CREATE DATABASE db_library;创建名称为db_library的数据库。
2.通过CREATE SCHEMA db_library1;创建名称为db_library1的数据库。
3.通过mysql> CREATE DATABASE db_library_gbk -> CHARACTER SET = GBK;指定其字符集为GBK。
4.通过CREATE DATABASE IF NOT EXISTS db_library2;判断该数据库名称是否存在,只有在不存在时才创建。
二、查看数据库
1.使用SHOW DATABASES;语句查看Mysql服务器中所有数据库名称。
mysql> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | db_database13 | | db_library | | db_library1 | | db_library2 | | db_library_gbk | | hotel | | mybatis | | mysql | | mysqldb | | performance_schema | | se | | spring | | springapp | | sys | | test | +--------------------+ 16 rows in set (0.01 sec)
三、选择名称为db_library的数据库,设置其为当前默认的数据库
mysql> USE db_library; Database changed
四、修改数据库db_library1,设置默认字符集为GBK和校对规则为简体中文
mysql> ALTER DATABASES db_library1 -> DEFAULT CHARACTER SET gbk -> DEFAULT CHARACTER SET gbk^C mysql> ALTER DATABASE db_library1 -> DEFAULT CHARACTER SET gbk -> DEFAULT COLLATE gbk_chinese_ci; Query OK, 1 row affected (0.00 sec)
五、删除数据库
mysql> DROP DATABASE db_library2; Query OK, 0 rows affected (0.01 sec) mysql> SHOW DATABASES; +--------------------+ | Database | +--------------------+ | information_schema | | db_database13 | | db_library | | db_library1 | | db_library_gbk | | hotel | | mybatis | | mysql | | mysqldb | | performance_schema | | se | | spring | | springapp | | sys | | test | +--------------------+ 15 rows in set (0.00 sec)
六、数据库存储引擎
存储引擎其实就是存储数据,为存储的数据建立索引,以及更新、查询数据等技术的实现方法。因为在关系数据库中数据是以表的形式存储的,所以存储引擎也可以成为表类型。
1.查询支持的全部存储引擎
mysql> SHOW ENGINES \G *************************** 1. row *************************** Engine: InnoDB Support: DEFAULT Comment: Supports transactions, row-level locking, and foreign keys Transactions: YES XA: YES Savepoints: YES *************************** 2. row *************************** Engine: MRG_MYISAM Support: YES Comment: Collection of identical MyISAM tables Transactions: NO XA: NO Savepoints: NO *************************** 3. row *************************** Engine: MEMORY Support: YES Comment: Hash based, stored in memory, useful for temporary tables Transactions: NO XA: NO Savepoints: NO *************************** 4. row *************************** Engine: BLACKHOLE Support: YES Comment: /dev/null storage engine (anything you write to it disappears) Transactions: NO XA: NO Savepoints: NO *************************** 5. row *************************** Engine: MyISAM Support: YES Comment: MyISAM storage engine Transactions: NO XA: NO Savepoints: NO *************************** 6. row *************************** Engine: CSV Support: YES Comment: CSV storage engine Transactions: NO XA: NO Savepoints: NO *************************** 7. row *************************** Engine: ARCHIVE Support: YES Comment: Archive storage engine Transactions: NO XA: NO Savepoints: NO *************************** 8. row *************************** Engine: PERFORMANCE_SCHEMA Support: YES Comment: Performance Schema Transactions: NO XA: NO Savepoints: NO *************************** 9. row *************************** Engine: FEDERATED Support: NO Comment: Federated MySQL storage engine Transactions: NULL XA: NULL Savepoints: NULL 9 rows in set (0.00 sec)
2.查询默认的存储引擎,为InnoDB。
mysql> SHOW VARIABLES LIKE '%storage_engine%'; +----------------------------------+--------+ | Variable_name | Value | +----------------------------------+--------+ | default_storage_engine | InnoDB | | default_tmp_storage_engine | InnoDB | | disabled_storage_engines | | | internal_tmp_disk_storage_engine | InnoDB | +----------------------------------+--------+ 4 rows in set, 1 warning (0.01 sec)
3.InnoDB存储引擎
优势在于提供了良好的事务管理、崩溃修复能力和并发控制。缺点是其读写速率稍差,占用的数据空间比较大。
4.MylSAM存储引擎
优势在于占用空间小,处理速度快。缺点是不支持事务的完整性和并发性。
5.MEMORY存储引擎
大小受限,其存在于内存中的特性使得这类表的处理速度非常快,但是其数据易丢失,声明周期短。
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