SQL and NoSQL Databases

What is a Database?

A database is a

What is SQL?

SQL stands for Structured Query Language. An SQL database is a relational database meaning that data is stored in tables, records, in which relationships between tables are well defined. This means that tables can retrieve data from other tables.

Think of a table as a collection of people, each person being an entry or "record" in the table. There may be one table named "Engineering Students" and another table named "UWaterloo Clubs". These are collections of people and clubs, respectively. A student part of "Engineering Students" can also relate to multiple clubs under the "UWaterloo Clubs" table. This is called a one to many relation. In general, there are multiple different dependencies:

1. One to One: one record relates to another record in another table
2. One to Many: one record relates to many records in another table
3. Many to One: many records relate to another table record
4. Many to Many: many table records relate to many other table records in another table

SQL & Relational Database Terminology

Word	Plain English
table	a set of data elements, containing columns of data fields and rows of entries
record (or row)	an entry to the table; an instance of what the table is collecting, with necessary fields
column	vertical grouping on table; indicates the fields in a given table
field	a single data structure for a single piece of data

MySQL Examples:

Showing the columns of a MySQL database SHOW COLUMNS FROMplayers_two`;

+---------------------------+-------------+------+-----+---------+-------------------+ | Field | Type | Null | Key | Default | Extra | +---------------------------+-------------+------+-----+---------+-------------------+ | id | int(11) | NO | PRI | NULL | STORED GENERATED | | player_and_games | json | NO | | NULL | | | names_virtual | varchar(20) | NO | MUL | NULL | VIRTUAL GENERATED | | times_virtual | int(11) | NO | MUL | NULL | VIRTUAL GENERATED | | tennis_won_virtual | int(11) | NO | MUL | NULL | VIRTUAL GENERATED | | tennis_lost_virtual | int(11) | NO | MUL | NULL | VIRTUAL GENERATED | | battlefield_level_virtual | int(11) | NO | MUL | NULL | VIRTUAL GENERATED | +---------------------------+-------------+------+-----+---------+-------------------+ `

A more complex query... SELECTid, names_virtual, tennis_won_virtual, battlefield_level_virtual, times_virtualFROMplayers WHERE (battlefield_level_virtual> 50 AND tennis_won_virtual> 50) ORDER BYtimes_virtual` ASC;

+----+---------------+--------------------+---------------------------+---------------+ | id | names_virtual | tennis_won_virtual | battlefield_level_virtual | times_virtual | +----+---------------+--------------------+---------------------------+---------------+ | 5 | Phil | 130 | 98 | 7 | | 6 | Henry | 68 | 87 | 17 | +----+---------------+--------------------+---------------------------+---------------+ `

What is NoSQL?

A NoSQL database is a non-relational database meaning that

NoSQL Examples:

Database Terminology & Concepts [1]

SQL/Relational Database Term	NoSQL/MongoDB Term
database	database
table	collection
row	document/BSON document
column	field

References

• [1] Wikipedia (https://en.wikipedia.org/wiki/Relational_database)