SQL recursive query same table - sql

Question

I have a situation where I have to extract data from a non well designed database.
I have two tables
tableA
+----+----------+-----+---------+
| ID | NAME | AGE | UNIT_ID |
+----+----------+-----+---------+
| 1 | Brown | 25 | 50 |
| 2 | White | 27 | 100 |
| 3 | Gilmour | 24 | 150 |
+----+----------+-----+---------+
tableB
+-----+----------+--------+--------+
| ID | DESC | ID_LV1 | ID_LV2 |
+-----+----------+--------+--------+
| 20 | Unit_20 | 20 | 40 |
| 40 | Unit_40 | 40 | 50 |
| 50 | Unit_50 | 100 | 40 |
| 100 | Unit_100 | 100 | 50 |
| 150 | Unit_150 | 50 | 20 |
+-----+----------+--------+--------+
ID_LV1 and ID_LV2 are linked to ID of the same table (tableB)
The goal is to run a query and get these results:
+----+----------+-----+-----------+-----------+-----------+
| ID | NAME | AGE | UNIT_DESC | LV1_DESC | LV2_DESC |
+----+----------+-----+-----------+-----------+-----------+
| 1 | Brown | 25 | Unit_50 | Unit_100 | Unit_40 |
| 2 | White | 27 | Unit_100 | Unit_100 | Unit_50 |
| 3 | Gilmour | 24 | Unit_150 | Unit_50 | Unit_20 |
+----+----------+-----+-----------+-----------+-----------+
My SQL is pretty rusty. The SQL server that I'm working with doesn't allow me to create views.
My last chance is to import in excel and run a vlookup :-)!

Answer 1

You can achieve your desired result simply using inner join
create table tableA( ID int, NAME varchar(100), AGE int, UNIT_ID int);
insert into tableA values( 1 , 'Brown' , 25 , 50 );
insert into tableA values( 2 , 'White' , 27 , 100 );
insert into tableA values( 3 , 'Gilmour' , 24 , 150 );
create table tableB( ID INT, DESCRIPTION VARCHAR(100), ID_LV1 INT, ID_LV2 INT);
INSERT INTO tableB values( 20 , 'Unit_20' , 20 , 40 );
INSERT INTO tableB values( 40 , 'Unit_40' , 40 , 50 );
INSERT INTO tableB values( 50 , 'Unit_50' ,100 , 40 );
INSERT INTO tableB values( 100 , 'Unit_100' , 100 , 50 );
INSERT INTO tableB values( 150 , 'Unit_150' , 50 , 20 );
Query:
select a.ID, a.Name, a.Age,b.Description, b_lv1.Description, b_lv2.Description from tableA a
inner join tableB b on a.UNIT_ID=b.ID
inner join tableB b_lv1 on b.ID_LV1=b_lv1.ID
inner join tableB b_lv2 on b.ID_LV2=b_lv2.ID
order by a.ID
Output:
ID
Name
Age
Description
Description
Description
1
Brown
25
Unit_50
Unit_100
Unit_40
2
White
27
Unit_100
Unit_100
Unit_50
3
Gilmour
24
Unit_150
Unit_50
Unit_20
db<>fiddle here