Append parent table column value to child table column in sql - sql-server

Question

Assume I have two tables, as below:
Table 1
ID Name
------------------
1 Adam
2 Eve
Table 2
ID FK_ID (Table 1) Name
--------------------------------------------
1 1 Chris
2 1 Austin
3 1 Steve
4 2 Charles
5 2 Erik
6 2 Austin
Required table as Result
ID Name
-----------------
1 Chris
2 Austin Adam
3 Steve
4 Charles
5 Erik
6 Austin Eve
Notice here, in the resulting table I want repeated "Austin" appended with "Adam/Eve" from parent table (i.e. Table 1), depending on "FK_ID". I want to do this in SQL. Any idea/help would really be appreciated.

Answer 1

You can use GROUP BY Name to check names with count(*) > 1 and then do a LEFT JOIN to append T1 names appropriately
Sample Data
CREATE TABLE Table1
([ID] int, [Name] varchar(4));
INSERT INTO Table1
([ID], [Name])
VALUES
(1, 'Adam'),
(2, 'Eve');
CREATE TABLE Table2
([ID] int, [FK_ID] int, [Name] varchar(7));
INSERT INTO Table2
([ID], [FK_ID], [Name])
VALUES
(1, 1, 'Chris'),
(2, 1, 'Austin'),
(3, 1, 'Steve'),
(4, 2, 'Charles'),
(5, 2, 'Erik'),
(6, 2, 'Austin');
Query
SELECT
T2.ID,
T2.Name + CASE WHEN T3.Name IS NOT NULL THEN ' ' + T1.Name ELSE '' END as Name
FROM Table2 T2
INNER JOIN Table1 T1 ON T2.[FK_ID] = T1.id
LEFT JOIN (SELECT Name FROM Table2 GROUP BY Name HAVING COUNT(*) > 1) T3 ON T2.Name = T3.Name
Output
ID Name
1 Chris
2 Austin Adam
3 Steve
4 Charles
5 Erik
6 Austin Eve

Answer 2

You can use a window count to determine whether a name is repeated or not:
SELECT t2.ID,
CONCAT(t2.Name,
IIF(COUNT(t2.Name) OVER(PARTITION BY t2.Name) > 1,
COALESCE(' ' + t1.Name, ''),
''))
FROM TABLE2 AS t2
LEFT JOIN TABLE1 AS t1 ON t2.FK_ID = t1.ID

Answer 3

SELECT ID,NAME
FROM TABLE2
WHERE NAME NOT IN (
SELECT NAME
FROM TABLE2
GROUP BY NAME
HAVING COUNT(*) >1 )
UNION
SELECT A.ID AS ID,A.NAME+' '+B.NAME AS NAME
FROM TABLE2 AS A INNER JOIN TABLE1 AS B
ON A.FK_ID = B.ID
WHERE NAME IN (
SELECT NAME
FROM TABLE2
GROUP BY NAME
HAVING COUNT(*) >1 )
ORDER BY ID
Using union to process the logic by two group.