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Commonly confused · Data & Analytics

SQL vs NoSQL: What's the Difference?

SQL databases store data in tables with predefined schemas and relationships, queried with SQL and typically offering strong ACID transactions. NoSQL databases use flexible models such as documents, key-value pairs, wide columns, or graphs, and generally scale out horizontally for large or fast-changing data.

SQL (Relational) Databases

vs

NoSQL Databases

SQL (Relational) DatabasesNoSQL Databases
Data modelTables of rows and columnsDocument, key-value, wide-column, or graph
SchemaFixed, defined up front (schema on write)Flexible or schemaless
ScalingTraditionally verticalDesigned for horizontal scale out
ConsistencyStrong ACID transactionsOften eventual consistency (BASE), tunable
Query languageSQLVaries by product (APIs, MQL, CQL)
ExamplesMySQL, PostgreSQL, SQL Server, OracleMongoDB, Cassandra, Redis, DynamoDB, Neo4j
Best forTransactions, complex joins, structured dataLarge scale, rapid change, semi-structured data
Remember it

SQL is a spreadsheet with strict rules; NoSQL is a filing cabinet that takes any shape.

Exam tip

Questions describe a workload and ask for the database type: financial transactions with joins point to relational, while flexible JSON documents or massive key-value lookups point to NoSQL.

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