sql语句查询数据库表结构信息

开发中经常用到查询指定表及其字段的信息，以下是我整理的SQL语句查询方法，供自己平时使用也提供给大家参考！

1.适用MS SQL SERVER:

 SELECT
 表名 = case when a.colorder= then d.name else '' end,
 表说明 = case when a.colorder= then isnull(f.value,'') else '' end,
 字段序号 = a.colorder,
 字段名 = a.name,
 标识 = case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')= then '√'else '' end,
 主键 = case when exists(SELECT  FROM sysobjects where xtype='PK' and parent_obj=a.id 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'),),
 允许空 = case when a.isnullable= 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.xusertype=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
 sys.extended_properties g
 on
 --a.id=g.id and a.colid=g.smallid
 a.id=g.major_id and a.colid=g.Minor_id
 left join
 sys.extended_properties f
 on
 --d.id=f.id and f.smallid=
 d.id=f.major_id and f.Minor_id=
 where
 d.name='表名' --如果只查询指定表,加上此条件
 order by
 a.id,a.colorder

2.适用ORACLE:

 SELECT
 USER_TAB_COLS.TABLE_NAME as 表名,
 user_tab_comments.comments as 表备注,
 USER_TAB_COLS.COLUMN_ID as 列序号,
 user_col_comments.comments as 列备注,
 USER_TAB_COLS.COLUMN_NAME as 列名 ,
 USER_TAB_COLS.DATA_TYPE as 数据类型,
 USER_TAB_COLS.DATA_LENGTH as 长度,
 USER_TAB_COLS.NULLABLE as 是否为空,
 user_cons_columns.constraint_name as 约束名,
 user_constraints.constraint_type as 主键
 FROM USER_TAB_COLS inner join user_col_comments on
 user_col_comments.TABLE_NAME=USER_TAB_COLS.TABLE_NAME
 and user_col_comments.COLUMN_NAME=USER_TAB_COLS.COLUMN_NAME
 INNER join user_cons_columns on user_cons_columns.table_name=USER_TAB_COLS.table_name
 INNER join user_constraints on user_constraints.table_name=USER_TAB_COLS.table_name and user_constraints.constraint_name=user_cons_columns.constraint_name
 inner join user_tab_comments on USER_TAB_COLS.TABLE_NAME=user_tab_comments.TABLE_NAME
 WHERE USER_TAB_COLS.table_name='表名'
 ORDER BY USER_TAB_COLS.TABLE_NAME

原文其它网址：http://www.zuowenjun.cn/post/2014/08/28/26.html