--值类型转换select Convert(decimal,1.8*60)--时间差select datediff(minute,DATEADD(HOUR,-24,GETDATE()),GETDATE())--加减指定时间select DATEADD(HOUR,-24,GETDATE())--获取系统日期select GETDATE()--生成不重复Idselect NEWID()--转换小写select LOWER(NEWID())--转换大写select UPPER(NEWID())--前2个字select LEFT('123456789',2)--后2个字select RIGHT('123456789',2)--替换指定字符select replace('abc','ab','你好')--最大值 Max(字段名)select Max(999) as 最大值--最小值 Min(字段名)select Min(1) as 最小值--总值 Sum(字段名)select Sum(100) as 总值--判断null转换成指定值select isnull(111,100) as 如果null就显示第二个参数反之显示第一个--查询非重复字段值SELECT DISTINCT property FROM table--表总条数SELECT count(*) as 总条数 FROM table--查找重复数据select GUID from tablegroup by GUID having count(*)>(select top 1 count(GUID) as counts from table group by GUID order by counts desc)--删除重复数据，只保留第一次插入的行。delete tablewhere GUID in(select GUID from tablegroup by GUID having count(*)>(select top 1 count(GUID) as counts from table group by GUID order by counts desc)) and property1=property2--排序(asc:默认值,升序;desc:降序;)SELECT DISTINCT property FROM table order by property desc--生成随机数（0~100之间任一整数）select CAST(FLOOR(RAND()*101)AS int)--判断字段值，不同情况返回不同值select (case 1 when 1 then '基数' when 2 then '偶数' when 0 then '零' else '99' end)select (case when 1=1 then '基数' when 2=2 then '偶数' when 0=0 then '零' else '99' end)--cmd.exe下SQL服务启动码：net start mssqlserver--cmd.exe下SQL服务停止码：net stop mssqlserver