• T-SQL实用查询之常用SQL语句


    删除数据库所有的表:

    declare @sql varchar(8000) 
    while (select count(*) from sysobjects where type='U')>0 
    begin 
    SELECT @sql='drop table ' + name 
    FROM sysobjects 
    WHERE (type = 'U') 
    ORDER BY 'drop table ' + name 
    exec(@sql) 
    end

     查询表的字段信息:

    SELECT (case when a.colorder=1 then d.name else null end) 表名, 
    a.colorder 字段序号,a.name 字段名,
    (case when COLUMNPROPERTY( a.id,a.name,'IsIdentity')=1 then '√'else '' end) 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) 主键,b.name 类型,a.length 占用字节数, 
     COLUMNPROPERTY(a.id,a.name,'PRECISION') as 长度, 
     isnull(COLUMNPROPERTY(a.id,a.name,'Scale'),0) as 小数位数,(case when a.isnullable=1 then '√'else '' end) 允许空, 
     isnull(e.text,'') 默认值,isnull(g.[value], ' ') AS [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 sys.extended_properties g on a.id=g.major_id AND a.colid=g.minor_id
     left join sys.extended_properties f on d.id=f.class and f.minor_id=0
     where b.name is not null
     and d.name='tablename' 
     order by a.id,a.colorder
    

    http://jingyan.baidu.com/article/9c69d48f99a91b13c9024ebf.html

    判断字段是否包含中文字符:

     ---一个中文字符占2个字节
     select len(Type),datalength(Type),type from T_Visas where len(Type)=datalength(Type)

     查询表中的某个列是否有重复值出现的sql语句

    select 某列,COUNT(1) from table group by 某列 order by count(1)

     

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    根据索引条件查询结果与原表关联的查询
  • 原文地址:https://www.cnblogs.com/coce/p/5026581.html
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