在 SQL 中，如何将一个表的多个列中的多个外键 ID 连接到另一个表中的单个主键和唯一的 select 一个？

Question

Table A: Patient Encounters With Linked Diagnoses(DX)

Encounter_ID	Date	Primary_DX	DX_2	DX_3	DX_4
11111	01/01/2020	234234	256756	254537	678688
11112	05/01/2020	344564	234553	6786667	234234
11113	01/01/2022	123233	656444	678688	535465
11114	01/01/2021	435345	666654	3453453	456448

Table B : Diagnoses(DX) Code Linked with Their respective ICD Code

NOTE: The codes for this table is filtered for DX_ID / ICD_CODE 's specifically for heart disease.

DX_ID	ICD_CODE
234234	N123.42
344564	N45.32
234553	N153.24
678688	N365.34

I seek to get only the encounters with the following condition:

At least one of the Primary_DX, DX_2,DX_3,DX_4 codes in Table A is a heart disease, that is, their respective diagnosis code can be linked to table B.

From this list, I seek to only get the ICD_Code for only that heart disease diagnosis code .

I have to do this in two steps:

1. Get all encounters where at least one of the DX_code in Table A is a DX_Code in Table B.

2. From this temporary table, select only the heart disease code and retrieve the ICD_code . If there are multiple heart disease for a single encounter, then they will show up as two separate rows.

So final output could have the following format:

Encounter_ID	ICD_CODE
11111	N123.42
11111	N45.32
11112	N123.42
11115	N15.42
11114	N123.42

Now filter for heart disease dx_codes with the EXISTS cause as below:

SELECT
    Enounter_ID,
    Primary_DX,
    DX_2,
    DX_3,
    DX_4,
FROM 
    TABLE_A
WHERE   
    EXISTS (SELECT 1 FROM TABLE_B)

But I am getting encounters where NONE of the linked diagnoses are from the heart disease table.

Answer 1

Wouldn't this be enough?

select Encounter_ID, ICD_CODE 
  from Table_A, Table_B
 where Primary_DX = DX_ID
    or DX_2 = DX_ID
    or DX_3 = DX_ID
    or DX_4 = DX_ID
order by Encounter_ID