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mysql lEFt join 重复

你的d表,a表和b表的关联字段在做join之前要保证唯一性.. 比如 left join (select distinct bizArea,cntNo from crm_contractbaseinfo) a on c.crtNO=a.cntNo

select distinct id,name,mobile,city from table1 left join table2 on table1.id = table2.table1_id;

重复来自关联 条件了。 如果你用 A left join B on A.t1=B.t2 在B表中t2 有多条,那么你的结果 就会 变成多条了 和你 用 form A,B where A.t1=B.t2 是一样的道理 如A t1 字段 1 2 3 4 B t2 字段 1 ,1,2,2,3 你如果全连接 A.t1=B.t2 就是 A.t1 ...

明显是一对多吗 select * from 主 a left join 子 b on a.g_num=b.g_num

Sql代码 CREATE VIEW view_name AS SELECT t1.xxx, t2.xxx, t3.xxx FROM (table1 t1 INNER JOIN table2 t2 ON t1.fid = t2.fid) INNER JOIN table3 t3 ON t1.mid = t3.mid; 这里使用了3表关联,对于多表关联的 INNER JOIN 写法有一个技巧 1. 先...

select id,a.name,pass,userid,age,num from a left join b on a.name=b.name and a.id=''

(#计算成人人数 SELECT tb_sell_tbfinance.order_no AS order_no0, tb_sell_tbfinance.passenger_type AS passenger_type0, COUNT(*) AS passenger_count FROM tb_sell_tbfinance GROUP BY tb_sell_tbfinance.passenger_type, tb_sell_tbfinance...

用group_concat select name,name1,group_concat(name2) from (select province.name as name,city.name1 as name1,area.name2 as name2 from city left join province on city.provincecode=province.code left join area on area.citycode=cit...

select Sno,Sname,concat(Cname) as Cname from (select sc.Id ,s.Sname, c.Cname from SelectCourse scleft join Student s on s.Sno = sc.Sno left join Course c on c.Cid = sc.Cid) t group by Sno;

inner join 会兼顾两张表,应该是你另一个表里面那个主键的数据有两条;;;先确定主表,用left join 或者right join 就会只有一条了

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