Tag system implementation

Use RDBMS

Give below 2 tables:
Table: BOOK

BOOK_ID	BOOK_NAME	AUTHOR
1	JAVA	JASON
2	RUBY	JASON
3	PYTHON	JASON
4	PHP	JASON
5	OBJECTIVE-C	JASON
6	SWIFT	JASON

Table: TAG

TAG_ID	TAG_NAME	BOOK_ID
1	WEB	1
2	WEB	2
3	WEB	3
4	WEB	4
5	APPLE	5
6	APPLE	6
7	PHP	4

If we want to get the books which both have WEB and PHP tag, we need below SQL:

SELECT T1.BOOK_ID FROM TAG T1 INNER JOIN TAG T2 
        ON T1.BOOK_ID=T2.BOOK_ID AND T1.TAG_NAME='WEB' AND T2.TAG_NAME='PHP'; 

Use Redis

prepare the data:

set book;;bookid;;1;;title JAVA
set book;;bookid;;2;;title RUBY
set book;;bookid;;3;;title PYTHON
set book;;bookid;;4;;title PHP
set book;;bookid;;5;;title OBJECTIVE-C
set book;;bookid;;6;;title SWIFT

sadd tag;;WEB 1 2 3 4
sadd tag;;APPLE 5 6
sadd tag;;PHP 4

To get the book both have WEB and PHP tag, use below command:

sinter tag;;WEB tag;;PHP
> 4

e.g. for sinter:

key1 = {a,b,c,d}
key2 = {c}
key3 = {a,c,e}
SINTER key1 key2 key3 = {c}

To get the book either have WEB or PHP tag, use below command:

sunion tag;;WEB tag;;PHP
> 1 2 3 4

e.g. for sunion:

key1 = {a,b,c,d}
key2 = {c}
key3 = {a,c,e}
SUNION key1 key2 key3 = {a,b,c,d,e}