NoSQL database types (document, key-value, column, graph) in DBMS Theory - Step-by-Step Execution

Concept Flow - NoSQL database types (document, key-value, column, graph)

Start: Choose NoSQL type

↓

Use case decides best fit

You pick a NoSQL type based on data structure: documents, key-value pairs, columns, or graphs.

Execution Sample

DBMS Theory

INSERT INTO DocumentDB {"name": "Alice", "age": 30}
PUT KeyValueDB "user123" "Alice"
INSERT INTO ColumnDB (user_id, name) VALUES (123, "Alice")
CREATE NODE GraphDB (id:1, name:"Alice")
CREATE EDGE GraphDB (from:1, to:2, relation:"friend")

Shows how data is stored differently in each NoSQL type.

Analysis Table

Step	Database Type	Operation	Data Stored	Internal Structure	Result
1	Document	Insert	{"name": "Alice", "age": 30}	JSON-like document	Document stored with fields name and age
2	Key-Value	Put	Key: "user123", Value: "Alice"	Simple key-value pair	Key-value pair stored
3	Column	Insert	user_id=123, name="Alice"	Columns grouped in families	Row inserted with columns
4	Graph	Create Node	Node id=1, name="Alice"	Node with properties	Node created
5	Graph	Create Edge	Edge from node 1 to 2, relation="friend"	Edge connecting nodes	Edge created linking nodes
6	-	-	-	-	Execution ends after all inserts

💡 All data inserted into respective NoSQL database types

State Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	After Step 5	Final
DocumentDB	empty	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}	{"name": "Alice", "age": 30}
KeyValueDB	empty	empty	{"user123": "Alice"}	{"user123": "Alice"}	{"user123": "Alice"}	{"user123": "Alice"}	{"user123": "Alice"}
ColumnDB	empty	empty	empty	Row with user_id=123, name="Alice"	Row with user_id=123, name="Alice"	Row with user_id=123, name="Alice"	Row with user_id=123, name="Alice"
GraphDB Nodes	empty	empty	empty	Node 1: {name: "Alice"}	Node 1: {name: "Alice"}	Node 1: {name: "Alice"}	Node 1: {name: "Alice"}
GraphDB Edges	empty	empty	empty	empty	empty	Edge from 1 to 2: {relation: "friend"}	Edge from 1 to 2: {relation: "friend"}

Key Insights - 3 Insights

Why does the Document database store data as JSON-like documents instead of simple key-value pairs?

Because Document databases store complex, nested data with multiple fields in one document, unlike Key-Value databases which store only simple pairs. See execution_table rows 1 and 2.

How is data organized differently in Column databases compared to Document databases?

Column databases group data by columns in families for fast queries on specific columns, while Document databases store whole documents. See execution_table rows 1 and 3.

Why do Graph databases have nodes and edges instead of just storing data like other NoSQL types?

Graph databases model relationships explicitly with edges connecting nodes, which helps with connected data queries. See execution_table rows 4 and 5.

Visual Quiz - 3 Questions

Look at the execution_table at step 2. What kind of data is stored in the Key-Value database?

A A simple key and its associated value

B A JSON document with multiple fields

C Columns grouped in families

D Nodes and edges representing relationships

💡 Hint

Check the 'Data Stored' column at step 2 in execution_table

At which step does the Graph database create a connection between two nodes?

A Step 3

B Step 5

C Step 4

D Step 1

💡 Hint

Look for 'Create Edge' operation in execution_table

If you want to store user profiles with many fields and nested data, which NoSQL type from the table is best?

A Key-Value database

B Column database

C Document database

D Graph database

💡 Hint

See execution_table row 1 for storing complex data

Concept Snapshot

NoSQL databases store data differently:
- Document: JSON-like documents with fields
- Key-Value: simple key and value pairs
- Column: data in columns grouped by families
- Graph: nodes connected by edges
Choose type based on data shape and query needs.

Full Transcript

NoSQL databases come in four main types: document, key-value, column, and graph. Document databases store data as JSON-like documents with multiple fields, good for complex data. Key-value databases store simple pairs of keys and values, ideal for fast lookups. Column databases organize data by columns grouped in families, useful for queries on specific columns. Graph databases store nodes and edges to represent connected data and relationships. Each type suits different use cases depending on data structure and query patterns.

Practice

1. Which NoSQL database type is best suited for storing data as JSON-like documents with flexible schemas?

easy

A. Graph database

B. Document database

C. Column database

D. Key-value database

Solution

1. Step 1: Understand document database structure

   Document databases store data as documents, often JSON-like, allowing flexible and nested data.

2. Step 2: Compare with other NoSQL types

   Key-value stores use simple key-value pairs, column stores organize data by columns, and graph databases focus on relationships.

3. Final Answer:

   Document database -> Option B

4. Quick Check:

   Flexible JSON-like storage = Document database [OK]

Hint: JSON-like flexible data means document DB [OK]

Common Mistakes:

• Confusing key-value with document stores
• Thinking column stores handle JSON
• Assuming graph DB stores documents

2. Which of the following is the correct way to describe a key-value store?

easy

A. Stores data as nested JSON documents

B. Stores data as interconnected nodes and edges

C. Stores data in tables with rows and columns

D. Stores data as simple pairs of keys and values

Solution

1. Step 1: Define key-value store

   Key-value stores save data as pairs: a unique key and its associated value.

2. Step 2: Eliminate other options

   Nodes and edges describe graph DB, tables describe relational or column DB, nested JSON describes document DB.

3. Final Answer:

   Stores data as simple pairs of keys and values -> Option D

4. Quick Check:

   Key-value = key and value pairs [OK]

Hint: Key-value means simple pairs, not complex structures [OK]

Common Mistakes:

• Mixing graph DB with key-value store
• Confusing column DB with key-value
• Thinking document DB is key-value

3. Given a graph database storing people and their friendships, which query result would you expect from a query asking for all friends of 'Alice'?

medium

A. A set of nodes connected to 'Alice' by edges labeled 'friend'

B. A table with columns for friend names and ages

C. A list of key-value pairs with friend names

D. A JSON document containing Alice's profile

Solution

1. Step 1: Understand graph database query

   Graph DB queries return nodes and edges; friends of Alice are nodes connected by 'friend' edges.

2. Step 2: Compare expected outputs

   Key-value pairs or tables are not typical graph DB outputs; JSON document is for document DB.

3. Final Answer:

   A set of nodes connected to 'Alice' by edges labeled 'friend' -> Option A

4. Quick Check:

   Graph DB returns connected nodes and edges [OK]

Hint: Graph DB queries return nodes and edges, not tables or JSON [OK]

Common Mistakes:

• Expecting tabular output from graph DB
• Confusing document DB JSON with graph DB output
• Thinking key-value pairs represent graph edges

4. You wrote a query to retrieve data from a column-family NoSQL database but got an error. Which mistake likely caused this?

medium

A. Using nested JSON documents in the query

B. Querying nodes and edges instead of tables

C. Trying to access data by key only without specifying column family

D. Using key-value pairs without keys

Solution

1. Step 1: Understand column-family DB query requirements

   Column-family DBs require specifying column families to access data properly.

2. Step 2: Identify error cause

   Accessing data by key alone without column family causes errors; other options relate to different DB types or invalid syntax.

3. Final Answer:

   Trying to access data by key only without specifying column family -> Option C

4. Quick Check:

   Column DB needs column family in queries [OK]

Hint: Column DB queries must specify column family [OK]

Common Mistakes:

• Using document DB JSON syntax in column DB
• Ignoring column family in queries
• Confusing graph DB queries with column DB

5. You need to design a social network app that stores users, their posts, and complex friend relationships with recommendations. Which NoSQL database type should you choose and why?

hard

A. Graph database, because it efficiently manages complex relationships

B. Key-value database, because it is fastest for any data

C. Document database, because it handles nested posts well

D. Column database, because it stores large tables efficiently

Solution

1. Step 1: Analyze app data needs

   The app needs to store users, posts, and complex friend relationships with recommendations.

2. Step 2: Match database type to needs

   Graph DBs excel at managing complex relationships and traversals, ideal for social networks.

3. Step 3: Evaluate other options

   Document DB handles nested data but less efficient for relationships; key-value is simple but not relationship-focused; column DB is for wide tables, not relationships.

4. Final Answer:

   Graph database, because it efficiently manages complex relationships -> Option A

5. Quick Check:

   Complex relationships = Graph DB [OK]

Hint: Complex relationships? Choose graph DB [OK]

Common Mistakes:

• Choosing document DB for relationship-heavy data
• Assuming key-value is best for all speed needs
• Ignoring graph DB strengths in relationships