MySql常用的Sql语句

1、多表联级查询并分组

MySql数据库中

–1、查询重复数据–

select *, sum(1) as total from t_businessman group by longitude,latitude having total = 2;

–2、根据id查询重复数据详细信息—-

select * from t_baiduapi where businessman_id = 1406;

–3、 –先去除重复,去除后的数据将重新插入新表中,即就得到了没有重复后的数据了—-

INSERT INTO t_baiduapi select distinct * from table2 GROUP BY longitude,latitude;

–4、 –通过distinct关键字去除重复数据—-

select distinct * from t_businessman; where longitude = '39.808475' and latitude = '116.49746';

PS：distinct关键字儿在MySql好像是不起作用,所以只能用分组去除重复数据（ Group by ）!

–5、 –经纬度计算(来算出两地的距离)（荐）—-

–6、 –子查询—-

代码附上：1、

drop function if exists getDistance;  
DELIMITER $$    
CREATE DEFINER=`root`@`localhost` FUNCTION `getDistance`( lon1 float(10,7) ,lat1 float(10,7) ,lon2 float(10,7) ,lat2 float(10,7) ) RETURNS double begin declare d double;  
    declare radius int;  
    set radius = 6378140; #假设地球为正球形，直径为6378140米  
    set d = (2*ATAN2(SQRT(SIN((lat1-lat2)*PI()/180/2) *SIN((lat1-lat2)*PI()/180/2)+ COS(lat2*PI()/180)*COS(lat1*PI()/180) *SIN((lon1-lon2)*PI()/180/2) *SIN((lon1-lon2)*PI()/180/2)), SQRT(1-SIN((lat1-lat2)*PI()/180/2) *SIN((lat1-lat2)*PI()/180/2) +COS(lat2*PI()/180)*COS(lat1*PI()/180) *SIN((lon1-lon2)*PI()/180/2) *SIN((lon1-lon2)*PI()/180/2))))*radius;  
    return d;  
end $$ DELIMITER ;   
select getDistance(116.3899,39.91578,116.3904,39.91576); 

#查询数据  hotelinfo 表中的数据
2、
SELECT hotelinfo.id,hotelinfo.address, ROUND(getDistance(hotelinfo.longitude,hotelinfo.latitude,'116.354098','40.002223')) AS distance FROM hotelinfo having distance <10;

PS：查询数据的时候，尽量不要这样去查询，例如：

selcect * from student 

这样是不大合理的，导致执行效率问题。相信你的老师教过你这些！