如何在连接两个表的同时从第二个表获取前1行：SQL Server 2014

Question

I am new to SQL Server 2014. I am trying to get data from two tables by join.

In the second table, I have multiple values for the same Header ID. I want to take the TOP 1 row value from the second table:

I want to take the data as in the following format

I want to take the TOP 1 image for all the names in the first table.

Can anyone help me to solve this?

Answer 1

You can use cross apply . The conditions are a little unclear, but the idea is:

select t1.*, t2.images
from table1 t1 cross apply
     (select top (1) t2.*
      from t2
      where t2.? = t1.id
     ) t2;

I would speculate that the correlated condition should use either t2.h_id or t2.id .

Answer 2

Is that what are you looking for

WITH T1 AS
(
  SELECT 1 ID,
         'Anto' Name,
         'Manager' Position
  UNION
  SELECT 2, 
         'Nick',
         'CEO'
)
, T2 AS
(
  SELECT 1 ID,
         1 H_ID,
         'URL1' Images
  UNION
  SELECT 2,
         1,
         'URL2'
  UNION
  SELECT 3,
         1,
         'URL3'
)

SELECT *
FROM T1 CROSS JOIN (SELECT TOP 1 Images FROM T2 ORDER BY ID) TT

Demo

OR

SELECT TOP 1
       T1.*,
       T2.Images
FROM T1 INNER JOIN T2
ON T1.ID = T2.H_ID
ORDER BY T2.ID;

Answer 3

Try this one

SELECT *
FROM T1, T2
WHERE T1.ID = T2.H_ID
AND NOT EXISTS(
    SELECT * 
    FROM T2 as T2BIS -- just an alias table
    WHERE T2BIS.H_ID = T1.ID -- usual join
    AND T2.ID > T2BIS.ID --change operator to take the last instead of the first
)

This is a generic solution that you can use in many case when you adjust the subquery on where conditions and EXISTS / NOT EXISTS clause, just an camparison between two identical spaces, you define the conditions.

1. the first of something ...
2. the last of someting ...
3. everything higher than ...
4. etc...