sql server中系统表的作用

       1：获取当前数据库中的所有用户表

select Name from sysobjects where xtype='u' and status>=0

　　2：获取某一个表的所有字段

select name from syscolumns where id=object_id('表名')

　　3：查看与某一个表相关的视图、存储过程、函数

select a.* from sysobjects a, syscomments b where a.id = b.id and b.text like '%表名%'

　　4：查看当前数据库中所有存储过程

select name as 存储过程名称 from sysobjects where xtype='P'

　　5：查询用户创建的所有数据库

select * from master..sysdatabases D where sid not in(select sid from master..syslogins where name='sa')

　　或者

select dbid, name AS DB_NAME from master..sysdatabases where sid <> 0x01

　　6：查询某一个表的字段和数据类型

select column_name,data_type from information_schema.columns  where table_name = '表名'

 
       比如说有A表的一个主键，作为B、C、D表的外键，可能你在某些时候修改A表中的某个记录，也许这个记录被BCD表已经用到，要修改很麻烦，昨天写了几个sql语句可以方便的实现这个要求，不过下班走的急，没来得及这里整理，周一上班再看贴上，初步计划是还有一个主要的应用，是在做子母表删除的时候，应该可以写一个函数，传入主键ID，然后删除所有子表的该记录，下周一实现。
实现上边所说功能的俩存储过程

 1 -- 更新某主表下边对应的外键值
 2
 3 CREATE   PROCEDURE   Proc_UpdateFroeKeyVal
 4    @TblName   varchar ( 50 ),
 5    @FroeKeyName   varchar ( 50 ),
 6    @Value   varchar ( 50 )
 7    AS
 8
 9 BEGIN  
10    declare   @TblID   varchar ( 50 ),
11          @ColuID   varchar ( 50 )
12    select    @TblID   =  id  from   sysobjects  where  name  =   @TblName
13    select   @ColuID   =  colid  from  syscolumns  where  id  =   @TblID   and  name  =   ' UserID '
14
15        select  A. * ,B.Name  as  F_TblName,C.Name  as  F_ColName   into  #TmpTbl
16                    from  
17                      sysforeignkeys  as  A,sysobjects  as  B, syscolumns  as  C 
18                    where  
19                      A.rkeyid  =   @TblID
20                    And
21                      A.rkey  =   @ColuID
22                    And
23                      B.id  =  fkeyid
24                    And
25                      C.id  =  fkeyid
26                    And
27                      C.colid  =  fkey
28
29        declare   @tabname   varchar ( 40 ), @colName   varchar ( 20 ), @sqlStr   varchar ( 1024 )
30       
31        DECLARE  TabName_Cursor  CURSOR   FOR
32        SELECT  F_TblName, F_ColName  FROM  #TmpTbl
33        OPEN  TabName_Cursor
34        FETCH  TabName_Cursor  into   @tabname , @colName
35        WHILE   @@FETCH_STATUS   =   0
36        BEGIN
37           select   @sqlStr   = ' Update  ' + @tabname + '  Set   ' + @colName + '  = ' +  " ' "+@Value +" ' "
38           -- print @sqlstr
39           exec ( @sqlstr )
40           FETCH  TabName_Cursor  into    @tabname , @colName
41        END
42        CLOSE  TabName_Cursor
43        DEALLOCATE  TabName_Cursor
44 END
45 GO
46

继续

 1 -- 删除某主表对应子表记录
 2
 3 CREATE   PROCEDURE   Proc_DelFroeKeyVal
 4    @TblName   varchar ( 50 ),
 5    @FroeKeyName   varchar ( 50 ),
 6    @Value   varchar ( 50 )
 7    AS
 8
 9 BEGIN  
10    declare   @TblID   varchar ( 50 ),
11          @ColuID   varchar ( 50 )
12    select    @TblID   =  id  from   sysobjects  where  name  =   @TblName
13    -- select @TblID =OBJECT_ID ( 'T_User' )
14    select   @ColuID   =  colid  from  syscolumns  where  id  =   @TblID   and  name  =   ' UserID '
15
16        select  A. * ,B.Name  as  F_TblName,C.Name  as  F_ColName   into  #TmpTbl
17                    from  
18                      sysforeignkeys  as  A,sysobjects  as  B, syscolumns  as  C 
19                    where  
20                      A.rkeyid  =   @TblID
21                    And
22                      A.rkey  =   @ColuID
23                    And
24                      B.id  =  fkeyid
25                    And
26                      C.id  =  fkeyid
27                    And
28                      C.colid  =  fkey
29
30        declare   @tabname   varchar ( 40 ), @colName   varchar ( 20 ), @sqlStr   varchar ( 1024 )
31       
32        DECLARE  TabName_Cursor  CURSOR   FOR
33        SELECT  F_TblName, F_ColName  FROM  #TmpTbl
34        OPEN  TabName_Cursor
35        FETCH  TabName_Cursor  into   @tabname , @colName
36        WHILE   @@FETCH_STATUS   =   0
37        BEGIN
38           select   @sqlStr   = ' delete  ' + @tabname + '  where   ' + @colName + '  = ' +  " ' "+@Value +" ' "
39           -- print @sqlstr
40           exec ( @sqlstr )
41           FETCH  TabName_Cursor  into    @tabname , @colName
42        END
43        CLOSE  TabName_Cursor
44        DEALLOCATE  TabName_Cursor
45 END