给表添加主键：alter table 表名 add constraint 主键名 primary key(字段名)
如：alter table DC_ALARM add constraint PK_ALARMID primary key(ALARMID)
给表添加唯一键：alter table 表名 add constraint 唯一键名 unique(字段名)
如：alter table DC_FACTOR add constraint UQ_COLUMNCODE unique(COLUMNCODE)
给表添加外键：alter table 需要添加外键的表名 add constraint 外键名 foreign key(需要设置为外键的字段) references 被引用表表名(被引用字段)
alter table DC_APP_NOTICE add constraint FK_APP_NOTICE_USERID foreign key(id) references DC_USER(id)
drop INDEX idx_DC_ALARM_lookup ON DC_ALARM --删除索引
ALTER TABLE DC_ALARM ALTER COLUMN [ALARMID] varchar(50) not NULL; --设置某一列不为null
CREATE NONCLUSTERED INDEX idx_DC_ALARM_lookup ON DC_ALARM(ALARMID,MONITORTYPE)--创建非聚集索引
alter table DC_ALARM add constraint UQ_DC_ALARM unique (FACTORCODE,TIME,MONITORTYPE,VALUE,MN )--添加联合唯一键
select count (FACTOR),MONITORTYPE,MN from DC_ALARM_LIMIT group by FACTOR,MONITORTYPE,MN--查询重复行
DELETE FROM DC_ALARM_LIMIT where id not in (
select max(id) from DC_ALARM_LIMIT group by FACTOR,MONITORTYPE,MN
) --删除重复行中最大行外的所有行