PGSQL

毫秒值转换为年月

to_char(to_timestamp(createdtime/1000),'YYYY-MM')

毫秒值转换为年

to_char(to_timestamp(createdtime/1000),'YYYY')

毫秒值转换为年月日时分秒

to_char(to_timestamp(createdtime/1000),'YYYY-MM-DD  HH:MI:ss')

毫秒值转换为周几

 to_char(to_timestamp(createdtime/1000),'DAY')

详情见 Pgsql 官方手册

如查询每个月的工单分别有多少

select  to_char(to_timestamp(createdtime/1000),'yyyy-MM') as "创建时间",count(workorderid) from workorder group by "创建时间";

MSSQL 

通过year和month方法分别获取年和月，在字符串拼接在一起。

CAST(year(DATEADD(SECOND,operationtime/1000,'1970-1-1')) as varchar(4))+ '-'+CAST(month(DATEADD(SECOND,operationtime/1000,'1970-1-1')) as varchar(2)) as "变更时间"