求一句简单的sql语句

Question

有三张表:
employee, 列名为employeeid name
jobyear, 列名为employeeid, jobid, jobyearid
jobyearmonth, 列名为jobid, jobyearid, month我需要select出所有的jobyearmonth中的数据，而且前面加上name，请问应该怎么写？

Answer 1

select c.name,a.* 
from jobyearmonth a
left join jobyear b on a.jobyearid=b.jobyearid
left join employee c on b.employeeid=c.employeeid

Answer 2

select name,jobid, jobyearid, month from employee a,jobyear b,jobyearmonth c where a.employeeid = b.employeeid and b.jobyearid = c.jobyearid and b.jobid  = c.jobid

Answer 3

employee, 列名为employeeid name
jobyear, 列名为employeeid, jobid, jobyearid
jobyearmonth, 列名为jobid, jobyearid, month
select a.name,c.* from employee a left join jobyear b on a.employeeid=b.emloyeeid
                                  left join jobyearmonth c on b.jobid= c.jobid

Answer 4

select name,c.* from employee a,jobyear b,jobyearmonth c
where a.employeeid=b.employeeid and b.jobid=c.jobid and b.jobyearid=c.jobyearid

Answer 5

select employee.name ,jobid,jobyearid,month from jobyearmonth join jobyear on jobyearmonth .jobid=jobyear .jobid and jobyearmonth.jobyearid=jobyear.jobyearid join
employee on employee.employeeid=jobyear.employeeid

Answer 6

更正:
select employee.name ,jobyearmonth .jobid,jobyearmonth .jobyearid,jobyearmonth .month from jobyearmonth join jobyear on jobyearmonth .jobid=jobyear .jobid and jobyearmonth.jobyearid=jobyear.jobyearid join
employee on employee.employeeid=jobyear.employeeid

Answer 7

但是这样好像有重复的纪录
如果我直接select * from jobyearmonth,有28条纪录，但是如果一left join的话，就有52条纪录了

Answer 8

left join 会返回左边表所有的行