Joining tables without duplicate - sql

Question

I have 3 SQL tables as below:
Table 1
ItemId Name
----------
A aa
B bb
Table 2
ItemId Category
----------
A 1
A 2
A 3
B 1
Table 3
ItemId Dep
----------
A D1
B D2
B D3
I need result as this
ItemId Name Category Dep
------------------------
A aa 1 D1
2
3
B bb 1 D2
D3
Is there any way to get this result without looping tables?

Answer 1

You can first JOIN the tables on ItemId and then use ROW_NUMBER and RANK for formatting.
I suggest you do the display format in the client side
SQL Fiddle
WITH CTE AS(
SELECT
t1.ItemId, t1.Name, t2.Category, t3.Dep,
Rn_Cat = ROW_NUMBER() OVER(PARTITION BY t1.ItemId, t1.Name ORDER BY t2.Category),
Rn_Dep = ROW_NUMBER() OVER(PARTITION BY t1.ItemId, t1.Name ORDER BY t3.Dep),
Rnk_Cat = RANK() OVER(PARTITION BY t1.ItemId, t1.Name ORDER BY t2.Category),
Rnk_Dep = RANK() OVER(PARTITION BY t1.ItemId, t1.Name ORDER BY t3.Dep)
FROM Table1 t1
LEFT JOIN Table2 t2
ON t2.ItemId = t1.ItemId
LEFT JOIN Table3 t3
ON t3.ItemId = t1.ItemId
)
SELECT
ItemId = CASE WHEN Rn_Cat = 1 THEN ItemId ELSE '' END,
Name = CASE WHEN Rn_Cat = 1 THEN Name ELSE '' END,
Category = CASE WHEN Rn_Cat = Rnk_Cat THEN CONVERT(VARCHAR(10), Category) ELSE '' END,
Dep = CASE WHEN Rn_Dep = Rnk_Dep THEN CONVERT(VARCHAR(10), Dep) ELSE '' END
FROM CTE

Answer 2

May be Using UNION
Fiddle Here
WITH CTE AS(
SELECT
t2.ItemId,t1.Name,t2.Category,t3.Dep,
Rank() over(Partition by t1.ItemId,t1.Name order by t2.Category,t3.Dep) as rn
from
Table1 t1 join Table2 t2 on t1.ItemId=t2.ItemId
join Table3 t3 on t1.ItemId=t3.ItemId
)
SELECT
ItemId,Name,Category,Dep,Rn
FROM CTE where rn=1
union
SELECT
'','',Category,Dep,Rn
FROM CTE where rn>1

Answer 3

this will probably work:
;with cte_t1 as
(
select 'A' as ItemId, 'aa' as Name
union
select 'B' as ItemId, 'bb' as Name
),
cte_t2 as
(
select 'A' AS ItemId, 1 as Category
union
select 'A' AS ItemId, 2 as Category
union
select 'A' AS ItemId, 3 as Category
union
select 'B' AS ItemId, 1 as Category
),
cte_t3 as
(
select 'A' AS ItemId, 'D1' as Dep
union
select 'B' AS ItemId, 'D2' as Dep
union
select 'B' AS ItemId, 'D3' as Dep
),
cte_t4 as
(
SELECT T1.ItemId, t1.Name, T2.Category, T3.Dep, ROW_NUMBER() over(order by T1.ItemId, T2.Category) RowNumber
FROM cte_t1 t1 inner join cte_t2 t2
on t1.ItemId = t2.ItemId
inner join cte_t3 t3
on t1.ItemId = t3.ItemId
and t2.ItemId = t3.ItemId
)
select
case when a.ItemId = b.ItemId then '' else a.ItemId end as ItemId,
case when a.Name = b.Name then '' else a.Name end as Name,
case when a.Category = b.Category then '' else cast(a.Category as varchar(100)) end as Category,
case when a.Dep = b.Dep then '' else a.Dep end as Dep
from cte_t4 a
left join cte_t4 b
on a.RowNumber-1= b.RowNumber

Answer 4

Using this code -
SELECT table1.ItemID,
table1.Name,
table2.Category,
table3.Dep
FROM table1, table2, table3
WHERE table1.ItemID = table2.ItemID AND table1.ItemID = table3.ItemID;
produces this output -
+--------+------+----------+-----+
| ItemID | Name | Category | Dep |
+--------+------+----------+-----+
| A | aa | 1 | D1 |
| A | aa | 2 | D1 |
| A | aa | 3 | D1 |
| B | bb | 1 | D2 |
| B | bb | 1 | D3 |
+--------+------+----------+-----+
Is this what you are after, or do you wish to display a blank space for every repeat of a value?