sql server -连接空值

I have two tables. One has a list of links and the other one holds thier styles if available. The later is a sparse table, i.e. it does not have corresponding rows when their values are null. I run the following query:

我有两个表。一个有链接列表，另一个有自己的样式。后者是一个稀疏表，即当它们的值为空时，它没有相应的行。我运行以下查询:

select hl.*, hls.colorCode, hls.bold
from HeaderLinks hl, HeaderLinkStyles hls 
where hl.LinkId = hls.linkID
order by row asc, [column] asc

I want to modify this so that if a row does not exist for the specific record, these columns will receive null values in the result set.

我想对它进行修改，以便如果特定记录不存在行，这些列将在结果集中接收空值。

Thank you!

谢谢你！

5 个解决方案

#1

Left Join

左连接

Select hl.*, hls.colorCode, hls.bold 
From HeaderLinks hl
Left Join HeaderLinkStyles hls on hl.LinkId = hls.linkID
order by row asc,[column] ASC

#2

To get the NULL for not exist records you need to use either LEFT OUTER JOIN or RIGHT OUTER JOIN on the table.......

要获得无存在记录的NULL，您需要在表中使用左外连接或右外连接……

Select hl.*, hls.colorCode, hls.bold From HeaderLinks hl
Left Join HeaderLinkStyles hls on hl.LinkId = hls.linkID order by row asc,[column] ASC

Check joins over here : Visual Representation of SQL Joins

检查这里的连接:SQL连接的可视化表示

#3

A left or full join will fill a row with null when no match is found:

当没有找到匹配项时，左连接或全连接将用null填充一行:

select  *
from    HeaderLinks hl
full outer join
        HeaderLinkStyles hls 
on      hl.LinkId = hls.linkID 

A left join only fills the right hand table with nulls, a right join only the left hand table, and a full join fills both. For a visual illustration see A Visual Explanation of SQL Joins.

左连接仅用nulls填充右表，仅用左手表填充右连接，全连接填充这两个表。有关可视化的说明，请参阅SQL连接的可视化解释。

#4

You need to use left outer join

您需要使用左外部连接

select hl.*, hls.colorCode, hls.bold
from HeaderLinks hl
    left join HeaderLinkStyles hls on
      hl.LinkId = hls.linkID  
order by row asc, [column] asc

Using Outer Joins

使用外部连接

#5

You need to use LEFT JOIN

您需要使用左连接。

Select 
  hl.*, 
  hls.colorCode, 
  hls.bold 
from 
  HeaderLinks hl 
LEFT JOIN 
  HeaderLinkStyles hls on hl.LinkId = hls.linkID
order by 
  row asc,[column] ASC