Here is my current table structure for *tags*:

```
// tags
+----+------------+----------------------------------+----------+------------+
| id |    name    |            description           | used_num | date_time  |
+----+------------+----------------------------------+----------+------------+
| 1  | PHP        | some explanations for PHP        | 4234     | 1475028896 |
| 2  | SQL        | some explanations for SQL        | 734      | 1475048601 |
| 3  | jQuery     | some explanations for jQuery     | 434      | 1475068321 | 
| 4  | MySQL      | some explanations for MySQL      | 535      | 1475068332 |
| 5  | JavaScript | some explanations for JavaScript | 3325     | 1475071430 |
| 6  | HTML       | some explanations for HTML       | 2133     | 1475077842 |
| 7  | postgresql | some explanations for postgresql | 43       | 1475077851 |
+----+------------+----------------------------------+----------+------------+

```

As you know, some tags are related to each other. For example:

* `SQL`, `MySQL`, `postgresql`
* `JavaScript`, `jQuery`

are related ones in table above. How can I make that relation between them? Should I add one more column? Should it be containing what thing? *(since sometimes there are more than 2 related tags)*