sql server 列信息查询

在sqlserver中,常用的系统表有sysobjects,syscolumns, 这两个可以判断表是否存在,字段是否存在,可以满足一些需求的查询.但项目有需求,需要对比两张表的字段类型和长度是否相等,主要针对varchar,nvarchar类型的字段.这个时候就需要使用到另外一个视图 information_schema.columns . 该视图记录着表的列的详细信息.

以下为查询PROPOSAL表的列名相关信息

select  t2.TABLE_NAME,t2.COLUMN_NAME,t2.data_type,t2.character_maximum_length,
* FROM information_schema.columns t2
where table_name='proposal'

截图如下图

两表对比查询(proposal_history,proposal)

SELECT a.TABLE_NAME AS 表1,b.TABLE_NAME AS 表2,a.COLUMN_NAME AS 列名,
        a.DATA_TYPE AS 表1字段类型,b.DATA_TYPE AS 表2字段类型,
        a.CHARACTER_MAXIMUM_LENGTH AS 表1字段长度,
        b.CHARACTER_MAXIMUM_LENGTH AS 表2字段长度 
FROM 
    (select  t1.TABLE_NAME,t1.COLUMN_NAME,t1.data_type,ISNULL(t1.character_maximum_length,-1) AS CHARACTER_MAXIMUM_LENGTH
    from information_schema.columns t1
    where table_name='proposal_history')A
LEFT JOIN 
    (select  t2.TABLE_NAME,t2.COLUMN_NAME,t2.data_type,ISNULL(t2.character_maximum_length,-1) AS CHARACTER_MAXIMUM_LENGTH
    from information_schema.columns t2
    where table_name='proposal')B

ON a.COLUMN_NAME = b.COLUMN_NAME
WHERE 
(b.COLUMN_NAME IS NULL OR a.DATA_TYPE != b.DATA_TYPE OR a.CHARACTER_MAXIMUM_LENGTH ! = b.CHARACTER_MAXIMUM_LENGTH);

查询结果

以上表示 proposal_history 表比 proposal 多id,prp_version,create_time 三个字段.,并且两表的etitle字段类型不一致,分别为varchar,nvarchar. 调换两表位置,可以反着查.