1:利用SQL自带的存储过程

EXEC sp_pkeys @table_name='表名'

2:利用系统表INFORMATION_SCHEMA.KEY_COLUMN_USAGE

SELECT TABLE_NAME,COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE TABLE_NAME='表名'

3: 以下这个查询表结构的语句可能大家都见过：

利用syscolumns,sysindexes,sysindexkeys三个表关联可以查出主键

SELECT
 (case when a.colorder=1 then d.name else '' end) N'表名',
 a.colorder N'字段序号',
 a.name N'字段名',
 (case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end) N'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) N'主键',
 b.name N'类型',
 a.length N'占用字节数',
 COLUMNPROPERTY(a.id,a.name,'PRECISION') as N'长度',
 isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0) as N'小数位数',
 (case when a.isnullable=1 then '√'else '' end) N'允许空',
 isnull(e.text,'') N'默认值',
 isnull(g.[value],'') AS N'字段说明'
--into ##tx

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 sysproperties g
on a.id=g.id AND a.colid = g.smallid 
order by object_name(a.id),a.colorder

4:

select o.name as 表名,c.name as 字段名,k.colid as 字段序号,k.keyno as 索引顺序 from sysindexes i
join sysindexkeys k on i.id = k.id and i.indid = k.indid
join sysobjects o on i.id = o.id
join syscolumns c on i.id=c.id and k.colid = c.colid
where o.xtype = 'U'
and exists(select 1 from sysobjects where xtype = 'PK' and name = i.name)
order by o.name,k.colid