查询当前数据库名,表名
MySQL
1)显示所有数据库
show database;
2)显示所有表
show tables;
3)显示表结构
desc 表名
SQL Server
当前数据库名:
select db_name() as databasename
查询所有表:
select * from sysobjects where xtype='U'
某个数据库中所有的表名:
select name from sysobjects where xtype='u' order by name
查询表结构信息:
SELECT (case when a.colorder=1 then d.name else null end) 表名, a.colorder 字段序号,a.name 字段名, (case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end) 标识, (case when (SELECT count(*) FROM sysobjects WHERE (name in (SELECT name FROM sysindexes WHERE (id = a.id) AND (indid in (SELECT indid FROM sysindexkeys WHERE (id = a.id) AND (colid in (SELECT colid FROM syscolumns WHERE (id = a.id) AND (name = a.name))))))) AND (xtype = 'PK'))>0 then '√' else '' end) 主键,b.name 类型,a.length 占用字节数, COLUMNPROPERTY(a.id,a.name,'PRECISION') as 长度, isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0) as 小数位数,(case when a.isnullable=1 then '√'else '' end) 允许空, isnull(e.text,'') 默认值,isnull(g.[value], ' ') AS [说明] FROM syscolumns a left join systypes b on a.xtype=b.xusertype inner join sysobjects d on a.id=d.id and d.xtype='U' and d.name<>'dtproperties' left join syscomments e on a.cdefault=e.id left join sys.extended_properties g on a.id=g.major_id AND a.colid=g.minor_id left join sys.extended_properties f on d.id=f.class and f.minor_id=0 where b.name is not null --WHERE d.name='要查询的表' --如果只查询指定表,加上此条件 order by a.id,a.colorder
oracle
(1) 启动 监听
lsnrctl start;
(2)进入sqlplus界面
sqlplus /nolog
SQL>conn sys/jiaxiaoai@orcl as sysdba;
(3)启动数据库实例
SQL>startup;
(4)查看当前所有的数据库
select name from v$database;
(5)查看哪些用户拥有sysdba、sysoper权限
select * from V_$PWFILE_USERS;
show user;查看当前数据库连接用户
(6)进入某个数据库:database 数据库名;
查看数据库结构:desc v$database;
(7)查看所有用户实例:
select instance_name from v$instance;
(8)查看当前库的所有数据表
select table_name from all_tables;
select table_name from user_tables;
select table_name from all_tables where owner='用户名';
(9)查看表结构
desc 表名;
(10)增加数据库用户
create user 用户名 identified by 密码 default tablespace users Temporary TABLESPACE Temp;
(11)用户授权
grant connect,resource,dba to 用户名;
grant sysdba to 用户名;
(12)更改数据库用户密码
alter user 用户名 identified by 密码;