Sql server 级联查询 Left Join的应用

Sql server 级联查询 Left Join的应用

LEFT JOIN 关键字语法：

SELECT column_name(s) 
FROM table_name1
LEFT JOIN
table_name2  
ON 
table_name1.column_name=table_name2.column_name

高级应用：

SELECT  	
had.deptTypeId as deptTypeId
,hdt.typeName as deptTypeName
,had.id as deptID
,had.deptName as deptName
,isnull(sg.siteGoalPoint,0) as siteGoalPoint
,isnull(sg.supGoalPoint,0) as supGoalPoint

   
   
   
   

    
    
    
    

      from 
     
--单位 
     
(select a.deptTypeId,a.id,a.deptName 
     
 from HD_ACT_DEPT a 
     
 where 1 = 1 
     
 and deptTypeId = 'null' 
     
) as had 
     
LEFT JOIN 
     
--单位类型 
     
HD_DEPT_TYPE hdt 
     
ON had.deptTypeId = hdt.id 
     
LEFT JOIN 
     
--任务完成情况统计表 
     
(select a.siteGoalPoint,a.supGoalPoint,a.deptTypeId,a.deptID 
     
from cms_sup_submit_goal a 
     
where a.year = '2013' 
     
) as sg 
     
on had.deptTypeId = sg.deptTypeId and had.id = sg.deptID 
     
ORDER BY had.deptTypeId, had.id 
    
   
   
   
   

多表查询：

select s.id,s.name,s.sname from 

singer s, tb_su su

where s.id=su.sid  and  su.userid='1'