SQL系列学习(三) 获取Oracle、SqlServer、Access中表名、字段和主键

一、oracle

1、获取当前oracle数据库中的所有表

select table_name from user_tables

2、查询某个表中的字段名称、类型、精度、长度、是否为空  

select COLUMN_NAME,DATA_TYPE,DATA_PRECISION,DATA_SCALE,NULLABLE    
from user_tab_columns    
where table_name ='YourTableName'  

3、查询某个表中的主键字段名  

select col.column_name    
from user_constraints con,  user_cons_columns col    
where con.constraint_name = col.constraint_name    
and con.constraint_type='P'    
and col.table_name = 'YourTableName'  

4、查询某个表中的外键字段名称、所引用表名、所应用字段名  

select distinct(col.column_name),r.table_name,r.column_name    
from    
user_constraints con,   
user_cons_columns col,    
(select t2.table_name,t2.column_name,t1.r_constraint_name    
from user_constraints t1,user_cons_columns t2    
where t1.r_constraint_name=t2.constraint_name    
and t1.table_name='YourTableName'  
) r    
where con.constraint_name=col.constraint_name    
and con.r_constraint_name=r.r_constraint_name    
and con.table_name='YourTableName' 

二、SQLServer

1、读取库中的所有表名

select name from sysobjects where xtype='u' 

2、字段 

SELECT c.name,t.name,c.xprec,c.xscale,c.isnullable    
FROM systypes t,syscolumns c    
WHERE t.xtype=c.xtype    
AND c.id = (SELECT id FROM sysobjects WHERE name='YourTableName')    
ORDER BY c.colid   

3、主键（参考SqlServer系统存储过程sp_pkeys）  

SELECT     
表名=case 
when a.colorder=1 then d.name else '' end,     
字段名=a.name,     
标识=case when COLUMNPROPERTY(a.id,a.name,'IsIdentity')=1 then '√' else '' end,     
主键=case when exists(SELECT 1 FROM sysobjects where xtype= 'PK' and name in ( SELECT name FROM sysindexes WHERE indid in( SELECT indid FROM sysindexkeys WHERE id = a.id AND colid=a.colid ))) then '√' else '' end,     
类型=b.name,     
占用字节数=a.length,     
长度=COLUMNPROPERTY(a.id,a.name, 'PRECISION'),     
小数位数=isnull(COLUMNPROPERTY(a.id,a.name, 'Scale'),0),     
允许空=case when a.isnullable=1 then '√'else '' end,     
默认值=isnull(e.text, ''),     
字段说明=isnull(g.[value], '') 
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' 
--and d.name = '要查询的表名'
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 
and g.name='MS_Description' 
order by a.id,a.colorder 

4、外键  

select t1.name,t2.rtableName,t2.name    
from    
(select col.name, f.constid as temp    
from syscolumns col,sysforeignkeys f    
where f.fkeyid=col.id    
and f.fkey=col.colid    
and f.constid in    
( select distinct(id)     
   from sysobjects    
   where OBJECT_NAME(parent_obj)='YourTableName'    
   and xtype='F'    
  )    
) as t1 ,    
(select OBJECT_NAME(f.rkeyid) as rtableName,col.name, f.constid as temp    
from syscolumns col,sysforeignkeys f    
where f.rkeyid=col.id    
and f.rkey=col.colid    
and f.constid in    
( select distinct(id)    
   from sysobjects    
   where OBJECT_NAME(parent_obj)='YourTableName'    
   and xtype='F'    
)    
) as t2    
where t1.temp=t2.temp

三、Access

1、所有表清单

conn.Open();     
dt= conn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });

2、表结构

conn.Open();

dtColumnsInfo = conn.GetOleDbSchemaTable(OleDbSchemaGuid.Columns, new object[] { null, null, strTableName,null });