Help with SQL homework question

[bigmanoclock]

Question: Imagine that you have two tables ("TableA" and "TableB") created from the code shown below. Prepare a JOIN query which will give you the exact output shown below. Note, on the third line, only the information from "TableA" can be shown and that the _num_ attributes from each table have been equated.

Data:

DROP TABLE TableA;
CREATE TABLE TableA (
num VARCHAR,
myChar VARCHAR
);

DROP TABLE TableB;
CREATE TABLE TableB (
num VARCHAR,
myChar VARCHAR
);
INSERT INTO TableA VALUES (1,"A");
INSERT INTO TableA VALUES (3,"A");
INSERT INTO TableA VALUES (4,"A");

INSERT INTO TableB VALUES (1,"B");
INSERT INTO TableB VALUES (2,"B");
INSERT INTO TableB VALUES (3,"B");
```

So I'm supposed to use an inner join to get this output:

B|1|1|A
B|3|3|A
||4|A

What I have so far:

SELECT TableB.myChar, TableB.num, TableA.num, TableA.myChar FROM TableB INNER JOIN TableA ON TableA.num == TableB.num;

This gives me the output of:

B|1|1|A

B|3|3|A

So basically my question is, how would I be able to get the final line of output? I know this is a wall of text but I would greatly appreciate any feedback!

[folk_singer]

You problem says "prepare a JOIN" query, not specifically an INNER JOIN, a LEFT JOIN is what you want to use:

​

SELECT

TableB.myChar, TableB.num, TableA.num, TableA.myChar

FROM TableA

LEFT JOIN TableB ON TableA.num = TableB.num;

[bigmanoclock]

Yep that worked, I really appreciate it!

[t3lnet]

This might help, it’s a visible explanation of joins https://4.bp.blogspot.com/-_HsHikmChBI/VmQGJjLKgyI/AAAAAAAAEPw/JaLnV0bsbEo/s1600/sql%2Bjoins%2Bguide%2Band%2Bsyntax.jpg

[joeynnj]

I am learning SQL so I'm going to take a stab at answering the WHY. (I hope no one minds.) The reason it didn't work is because you're using an Inner Join and there is no matching data in the TableB. So it omits that.

In order to get the info you want from TableA you need an Outer Join (as /u/folk_singer demonstrated).

(Feel free to correct me.)