# 列出数据库

在本教程中，您将学习如何使用MySQL `SHOW DATABASES`命令列出MySQL数据库服务器中的所有数据库。

## 使用MySQL SHOW DATABASES

要列出MySQL服务器主机上的所有数据库，请使用`SHOW DATABASES`命令，如下所示：

```sql
SHOW DATABASES;
```

例如，要列出本地MySQL数据库服务器中的所有数据库，请首先登录到数据库服务器，如下所示：

```sql
C:\Users\Administrator>mysql -u root -p
Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 5.7.9 MySQL Community Server (GPL)

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>
```

然后使用`SHOW DATABASES`命令：

```sql
mysql> SHOW DATABASES;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| crmdb              |
| mysql              |
| newdb              |
| performance_schema |
| testdb             |
| yiibaidb           |
| yiibaidb_backup    |
+--------------------+
8 rows in set
```

`SHOW SCHEMAS`命令是`SHOW DATABASES`的同义词，因此以下命令将返回与上述相同的结果：

```sql
mysql> SHOW SCHEMAS;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| crmdb              |
| mysql              |
| newdb              |
| performance_schema |
| testdb             |
| yiibaidb           |
| yiibaidb_backup    |
+--------------------+
8 rows in set
```

如果要查询与特定模式匹配的数据库，请使用[LIKE](http://www.yiibai.com/mysql/like.html)子句，如下所示：

```sql
SHOW DATABASES LIKE pattern;
```

例如，以下语句返回以字符串“`schema`”结尾的数据库;

```sql
mysql> SHOW DATABASES LIKE '%schema';
+--------------------+
| Database (%schema) |
+--------------------+
| information_schema |
| performance_schema |
+--------------------+
2 rows in set
```

重要的是要注意，如果MySQL数据库服务器以`-skip-show-database`启动，则除非具有`SHOW DATABASES`权限，否则不能使用`SHOW DATABASES`语句。

## 从information\_schema查询数据库数据

如果`LIKE`子句中的条件不足，可以直接从`information_schema`数据库中的`schemata`表查询数据库信息。

例如，以下查询返回与`SHOW DATABASES`命令相同的结果。

```sql
SELECT schema_name 
FROM information_schema.schemata;
```

以下[SELECT](http://www.yiibai.com/mysql/select-statement-query-data.html)语句返回名称以’`schema`‘或’`db`‘结尾的数据库。

```sql
SELECT schema_name
FROM information_schema.schemata
WHERE schema_name LIKE '%schema' OR 
      schema_name LIKE '%db';
```

它返回以下结果集：

```sql
mysql> SELECT schema_name
FROM information_schema.schemata
WHERE schema_name LIKE '%schema' OR 
      schema_name LIKE '%db';
+--------------------+
| schema_name        |
+--------------------+
| information_schema |
| crmdb              |
| newdb              |
| performance_schema |
| testdb             |
| yiibaidb           |
+--------------------+
6 rows in set
```

在本教程中，您已经学习了如何使用`SHOW DATABASES`命令显示MySQL服务器中的所有数据库，或者从`information_schema`数据库中的`schemata`表进行查询。


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