SQL修改数据表字段长度

alter table m_Assysn_t nocheck CONSTRAINT all
Alter Table m_Assysn_t ALTER column ppid VARCHAR(150)
alter table m_Assysn_t check constraint all
Alter Table dbo.[T_STAT_ADMIN] ALTER column INIText VARCHAR(8000)
 

SUM操作的字符串到数值型的转换：

select sum(cast(变量 as bigint)) as 变量 from 表
例：select sum(cast(studentid as bigint)) as he from student