add basic join (inner join) example

[cindyuc]

Name: Xinyu Chen
Email: [email protected]
GTID: 903612905 % 14 = 13

Group 2, Topic 13: Write a toy C++ example to illustrate a basic join algorithm

For this topic, I implemented a simple join algorithm that utilizes inner join with hashmap.

There are 2 tables in the example:

student:

ID	Name	Age	Major
1	Alice	19	CS
2	Jonah	20	EE
3	Charlie	19	CS
4	David	22	EE
5	Eve	18	CS

grades:

ID	Course	Grade
1	CS101	A
1	EE200	B
2	CS101	C
4	EE200	B

After joining these 2 tables based on the ID that students.ID = grades.ID, we will get

ID	Name	Age	Major	ID	Course	Grade
1	Alice	19	CS	1	CS101	A
1	Alice	19	CS	1	EE200	B
2	Jonah	20	EE	2	CS101	C
4	David	22	EE	4	EE200	B

To run the unit tests, please use the following commands:

mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Debug  ..
make check
ctest -R innerjoin_test -V