sqlserver版：
查询当前数据库下所有表名：
select * from sys.tables;
查询当前库下，一张表的表名，字段名，字段类型，字段长度：
select a.name 表名,b.name 字段名,c.name 字段类型,c.length 字段长度 from sysobjects a,syscolumns b,systypes c where a.id=b.id
and a.name='DSE_SYS_DISTRICT' and a.xtype='U'
and b.xtype=c.xtype
删除所有表的外键约束*************************/
DECLARE c1 cursor for
select 'alter table ['+ object_name(parent_obj) + '] drop constraint ['+name+']; '
from sysobjects
where xtype = 'F'
open c1
declare @c1 varchar(8000)
fetch next from c1 into @c1
while(@@fetch_status=0)beginexec(@c1)
fetch next from c1 into @c1
endclose c1
deallocate c1
清空某个数据库所有表
use 数据库名(是要删除表的所在的那个数据库的名称)
GOdeclare @sql varchar(8000)
while (select count(*) from sysobjects where type='U')>0
beginSELECT @sql='drop table ' + name
FROM sysobjects
WHERE (type = 'U')
ORDER BY 'drop table ' + name
exec(@sql)
end