From relational to ledger

If you're an application developer, you might have some experience using a relational database management system (RDBMS) and Structured Query Language (SQL). As you begin working with Amazon QLDB, you will encounter many similarities. As you progress to more advanced topics, you will also encounter powerful new features that QLDB has built on the RDBMS foundation. This section describes common database components and operations, comparing and contrasting them with their equivalents in QLDB.

The following diagram shows the mapping constructs of the core components between a traditional RDBMS and Amazon QLDB.

The following table shows the primary high-level similarities and differences of built-in operational features between a traditional RDBMS and QLDB.

Operation	RDBMS	QLDB
Creating tables	CREATE TABLE statement that defines all column names and data types	CREATE TABLE statement that doesn't define any table attributes or data types to allow schemaless and open content
Creating indexes	CREATE INDEX statement	CREATE INDEX statement for any top-level fields on a table
Inserting data	INSERT statement that specifies values within a new row or tuple that adheres to the schema as defined by the table	INSERT statement that specifies values within a new document in any valid Amazon Ion format regardless of the existing documents in the table
Querying data	SELECT-FROM-WHERE statement	SELECT-FROM-WHERE statement in the same syntax as SQL when querying flat documents
Updating data	UPDATE-SET-WHERE statement	UPDATE-SET-WHERE statement in the same syntax as SQL when updating flat documents
Deleting data	DELETE-FROM-WHERE statement	DELETE-FROM-WHERE statement in the same syntax as SQL when deleting flat documents
Nested and semistructured data	Flat rows or tuples only	Documents that can have any structured, semistructured, or nested data as supported by the Amazon Ion data format and the PartiQL query language
Querying metadata	No built-in metadata	SELECT statement that queries from the built-in committed view of a table
Querying revision history	No built-in data history	SELECT statement that queries from the built-in history function
Cryptographic verification	No built-in cryptography or immutability	APIs that return a digest of a journal and a proof that verifies the integrity of any document revision relative to that digest

For an overview of the core concepts and terminology in QLDB, see Core concepts.

For detailed information about the process of creating, querying, and managing your data in a ledger, see Working with data and history.