a.mysql数据库
1.查询mysql中所有数据库名称
select SCHEMA_NAME from information_schema.SCHEMATA
2.查询mysql某个数据库下的所有表名
select TABLE_NAME FROM information_schema.TABLES where TABLE_SCHEMA = '数据库名'
3.授权用户可以在任何主机连接
grant all privileges on *.* to 'username'@'%' identified by 'password' with grant option;

b.sqlserver数据库
1.判断表中字段是否存在
select * from syscolumns where id = object_id('表名') and name = '字段名'
2.查询一个库中所有表名
select name from sysobjects where xtype = 'U' //and name like '%a%'