SQLITE3：当有数百列要转换时，将ID转换为代码

Question

I have a table A that has several hundred columns (let's say 301 for example) with the first column being the primary key and the rest being IDs from table B ie

CREATE TABLE "A" (
        ko_index_id INTEGER NOT NULL,
        ko1 INTEGER NOT NULL,
        ko2 INTEGER NOT NULL,
        ...
        ko300 INTEGER NOT NULL,
        PRIMARY KEY (ko_index_id)
);

CREATE TABLE "B" (
        id INTEGER NOT NULL,
        name INTEGER NOT NULL,
        PRIMARY KEY (id)
);

I would like to be able to convert the IDs into names. For example:

SELECT name FROM B WHERE id in (SELECT * FROM A);

Except the SELECT * part means that ko_index_id will be fed into B which is wrong. If there were only two columns in A I could just write

SELECT name FROM B WHERE id in (SELECT ko1, ko2 FROM A);

but table A has 300 columns!

Can anyone help me around this?

Answer 1

I agree with @Gordon's comment. If you can afford to change your data model, I would suggest you use an intersection table. It's the typical way to model "many-to-many" relationships in a database.

Example:

CREATE TABLE "A" (
        id INTEGER NOT NULL,
        ...
        PRIMARY KEY (id)
);

CREATE TABLE "B" (
        id INTEGER NOT NULL,
        name INTEGER NOT NULL,
        ...
        PRIMARY KEY (id)
);

CREATE TABLE "AB" (
        a_id INTEGER NOT NULL,
        b_id INTEGER NOT NULL
);

SELECT A.id, B.name 
FROM A
INNER JOIN AB ON A.id=AB.a_id
INNER JOIN B ON AB.b_id=B.id;

Answer 2

300+ columns? How about redoing table A by pivoting those columns into rows. You could have key name and value column. For example:

select * from A: 
id, ko_name, ko_value
1,  ko1, 5
1,  ko2, 6 

Then selecting the keys becomes much easier; eg:

SELECT name FROM B WHERE id in (SELECT ko_value FROM A where ko_name in ('ko1', 'ko2')) ;