多表查询
create table tb_department (
  DeptID varchar2(20) not null,
  deptName VARCHAR2(20) not null,
  deptAllowance NUMBER not null,
  Manager VARCHAR2(20) not null,
  deptTel NUMBER not null,
  constraint PK_DEPARTMENT primary key (DeptID)
);


create table tb_salary (
salID varchar2(20) primary key,
EmpID varchar2(20) unique references tb_employee(EmpID),
Salary NUMBER,
bonus NUMBER,
deduct NUMBER default 0
);


--加班
create table tb_Extrawork (
ewID varchar2(20) primary key,
  EmpID varchar(20) references tb_employee(EmpID),
  EwDate DATE ,
  EwConut NUMBER not null
);


--考勤
create table tb_Attendance (
  attID varchar2(20) primary key,
  AttDate DATE, 
  EmpID varchar2(20) references tb_employee(EmpID),  
ConutAtt NUMBER 
);


我想查出 tb_salary 表中所有字段 与empid =tb_department=tb_Extrawork=tb_Attendance中attdate与EwDate 在同一个月中的数据
----------------
 EmpID Salary bonus deduct EwDate AttDate ConutAtt deptAllowance EwConut  


我发现我对多表连接查询并不懂还希望你们给我点学习建议，谢谢

------解决方案--------------------

SQL code

select ts.EmpID,ts.Salary,ts.bonus,ts.deduct, 
       te.ewdate,te.EwConut,
       ta.attdate,ta.ConutAtt
from   tb_salary     ts,
       tb_Extrawork  te,
       tb_Attendance ta
where  ts.empid = te.empid
and    te.empid = ta.empid
and    to_char(te.EwDate,'MM') = to_char(ta.AttDate,'MM')
order by te.EwDate;

要得到deptAllowance信息需要通过employee表的depID去连tb_department.