获取SQL Server表字段的各种属性

其实，数据库的表、字段、索引、存储过程和触发器等等，都被称为数据库的对象。而关于这些对象的信息，都保存在SQL Server的系统表里面。我们可以通过查询这些表，来获取我们需要的数据库对象的信息。对于表的字段，我们可以通过一下SQL语句查询出它们的详细信息：
USE Northwind --数据库
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'
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 
WHERE
 d.name = 'Customers' --要查询的表
ORDER BY
 object_name(a.id), a.colorder