Join multiple tables using SQL & T-SQL - sql

Question

Unfortunately, I cannot be sure that the name of my question is correct here.
Example of initial data:
Table 1 Table 2 Table 3
| ID | Name | | ID | Info1 | | ID | Info2 |
|----|-------| |----|-------| |----|-------|
| 1 | Name1 | | 1 | text1 | | 1 | text1 |
| 2 | Name2 | | 1 | text1 | | 1 | text1 |
| 3 | Name3 | | 2 | text2 | | 1 | text1 |
| 2 | text2 | | 2 | text2 |
| 3 | text3 |
In my initial data I have relationship between 3 tables by field ID.
I need to join table2 and table3 to the first table, but if I do sequential join, like left join table2 and left join table3 by ID I will get additional records on second join, because there will be several records with one ID after first join.
I need to get records of table2 and table3 like a list in each column for ID of first table.
Here an example of expected result:
Table 3
| ID | Name |Info1(Table2)|Info2(Table3)|
|-------|-----------|-------------|-------------|
| 1 | Name1 | text1 | text1 |
| 1 | Name1 | text1 | text1 |
| 1 | Name1 | null | text1 |
| 2 | Name2 | text2 | text2 |
| 2 | Name2 | text2 | null |
| 3 | Name3 | null | text3 |

Answer 1

This is the method I would use, however, the table design you have could probably be improved on; why are Table2 and Table3 separate in the first place?
USE Sandbox;
GO
CREATE TABLE dbo.Table1 (ID int, [Name] varchar(5))
INSERT INTO dbo.Table1 (ID,
[Name])
VALUES(1,'Name1'),
(2,'Name1'),
(3,'Name3');
CREATE TABLE dbo.Table2 (Id int,Info1 varchar(5));
CREATE TABLE dbo.Table3 (Id int,Info2 varchar(5));
INSERT INTO dbo.Table2 (Id,
Info1)
VALUES(1,'text1'),
(1,'text1'),
(2,'text2'),
(2,'text2');
INSERT INTO dbo.Table3 (Id,
Info2)
VALUES(1,'text1'),
(1,'text1'),
(1,'text1'),
(2,'text2'),
(3,'text3');
WITH T2 AS(
SELECT ID,
Info1,
ROW_NUMBER() OVER (PARTITION BY ID ORDER BY (SELECT NULL)) AS RN --SELECT NULL as you have no other columns to actually create an order
FROM Table2),
T3 AS(
SELECT ID,
Info2,
ROW_NUMBER() OVER (PARTITION BY ID ORDER BY (SELECT NULL)) AS RN
FROM Table3),
Tally AS(
SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS I --Assuming you have 10 or less matching items
FROM (VALUES(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL),(NULL)) N(N))
SELECT T1.ID,
T1.[Name],
T2.info1,
T3.info2
FROM Table1 T1
CROSS JOIN Tally T
LEFT JOIN T2 ON T1.ID = T2.ID AND T.I = T2.RN
LEFT JOIN T3 ON T1.ID = T3.ID AND T.I = T3.RN
WHERE T2.ID IS NOT NULL OR T3.ID IS NOT NULL
ORDER BY T1.ID, T.I;
GO
DROP TABLE dbo.Table1;
DROP TABLE dbo.Table2;
DROP TABLE dbo.Table3;
If you have more than 10 rows, then you could build a "proper" tally table on the fly, or create a physical one. One on the fly is probably going to be a better idea though, as I doubt you're going to have 100's of matching rows.