SQL SERVER 查看数据库表的字段类型，是否允许为NULL，默认值，主键等

 declare @table_name   varchar(100)-- 表名  
 set @table_name='bqcform101'

--============表结构
    select 类别,表名or字段名,描述,字段类型,是否自增,允许为NULL,默认值 from   
    (  
    SELECT '表名' 类别,-1 column_id,tbs.name 表名or字段名,ds.value 描述,'' 字段类型,'' 是否自增,'' 允许为NULL,'' 默认值,1 rn  
    FROM sys.extended_properties ds    
    LEFT JOIN sysobjects tbs ON ds.major_id=tbs.id    
    WHERE  ds.minor_id=0 and tbs.name=@table_name  
    union  
    SELECT  
        @table_name 类别  
        ,c.column_id  
        ,C.name 表名or字段名  
        ,s.value 描述  
        ,字段类型 = T.name + CASE T.user_type_id WHEN 41 THEN '('+CAST(C.scale AS VARCHAR) +')'     -- time  
            WHEN 42 THEN '('+CAST(C.scale AS VARCHAR) +')'                                      -- datetime2  
            WHEN 43 THEN '('+CAST(C.scale AS VARCHAR) +')'                                      -- datetimeoffset  
            WHEN 106 THEN '('+CAST(C.precision  AS VARCHAR)+','+ CAST(C.scale AS VARCHAR) +')'  -- decimal  
            WHEN 108 THEN '('+CAST(C.precision  AS VARCHAR)+','+ CAST(C.scale AS VARCHAR) +')'  -- numeric  
            WHEN 165 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- varbinary  
            WHEN 167 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- varchar  
            WHEN 173 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- binary  
            WHEN 175 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- char  
            WHEN 231 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1)/2 AS VARCHAR),'MAX') +')'     -- nvarchar(该字段校检根据实际情况)  
            WHEN 239 THEN '('+ISNULL(CAST(NULLIF(C.max_length,-1) AS VARCHAR),'MAX') +')'       -- nchar  
            ELSE ''  
            END  
        ,case when C.is_identity=1 then '是' else '' end 是否自增
        --cast(C.is_identity as varchar(10)) 是否自增  
        ,case when C.is_nullable=1 then '是'else '' end 允许为NULL  
        ,默认值 = ISNULL(STUFF(LEFT(D.definition,LEN(D.definition)-1),1,1,''),'')   
        ,3 rn  
    FROM sys.columns C  
    INNER JOIN sys.types T ON C.user_type_id = T.user_type_id   
    LEFT JOIN sys.default_constraints D ON D.[object_id] =C.default_object_id AND D.parent_object_id = C.[object_id] AND D.parent_column_id = C.column_id   
    left join (select major_id,minor_id,value from sys.extended_properties) s on s.major_id = c.object_id and s.minor_id = c.column_id  
    WHERE C.[object_id] = OBJECT_ID(@table_name)  
    ) s   
    order by column_id,rn  

--============主键
select Primary_COLUMN_NAME = convert(sysname,c.name)                   
from                                                           
sysindexes i, syscolumns c, sysobjects o                       
where o.id = object_id(@table_name)                      
and o.id = c.id                                                
and o.id = i.id                                                
and (i.status & 0x800) = 0x800                                 
and (c.name = index_col (@table_name, i.indid,  1) or         
     c.name = index_col (@table_name, i.indid,  2) or         
     c.name = index_col (@table_name, i.indid,  3) or         
     c.name = index_col (@table_name, i.indid,  4) or         
     c.name = index_col (@table_name, i.indid,  5) or         
     c.name = index_col (@table_name, i.indid,  6) or         
     c.name = index_col (@table_name, i.indid,  7) or         
     c.name = index_col (@table_name, i.indid,  8) or         
     c.name = index_col (@table_name, i.indid,  9) or         
     c.name = index_col (@table_name, i.indid, 10) or         
     c.name = index_col (@table_name, i.indid, 11) or         
     c.name = index_col (@table_name, i.indid, 12) or         
     c.name = index_col (@table_name, i.indid, 13) or         
     c.name = index_col (@table_name, i.indid, 14) or         
     c.name = index_col (@table_name, i.indid, 15) or         
     c.name = index_col (@table_name, i.indid, 16)           
     )