SQL features

YugabyteDB's YSQL API reuses a fork of the query layer of PostgreSQL as its starting point and runs on top of YugabyteDB's distributed storage layer called DocDB. This architecture allows YSQL to support most PostgreSQL features, such as data types, queries, expressions, operators and functions, stored procedures, triggers, extensions, and so on, all of which are expected to work identically on both database systems.

{{< tip title="Tip" >}} A large portion of the documentation and examples written for PostgreSQL would work against YSQL.

{{< /tip >}}

The following diagram shows how YugabyteDB reuses the PostgreSQL query layer, specifically the components that receive the query (postman), the query parser, rewriter, and analyzer, as well as components responsible for planning and executing the query. Some of these components have been modified to perform efficiently in a distributed SQL database.

SQL features in YSQL

The following table lists the most important YSQL features which you would find familiar if you have worked with PostgreSQL.

YSQL Feature	Description
Schemas and Tables	SQL shell with ysqlsh, users, databases, tables, and schemas
Data Types	String, numeric, temporal types, SERIAL pseudo type, ENUM, arrays, composite types
DDL Statements	Data definition language
Data Manipulation	INSERT, UPDATE, DELETE, INSERT ... ON CONFLICT, and RETURNING clauses
Queries and Joins	Queries, joins, FROM, GROUP BY, HAVING clauses, common table expressions, recursive queries
Expressions and Operators	Basic operators and boolean, numeric, date expressions
Indexes	Support for indexes and constraints
Stored Procedures	Support for stored procedures
Triggers	Triggers (on data modification) and event triggers (on schema changes)
Extensions	Support for PostgreSQL extensions

Advanced features in YSQL

The following table lists the advanced features in YSQL.

YSQL Feature	Description
Cursors	Declaration of cursors in YSQL
Table Partitioning	List, range, and hash partitioning of tables
Views	Views and updatable views
Savepoints	Savepoints in YSQL
Collations	Collations in YSQL
Foreign data wrappers	Foreign data wrappers in YSQL

Going beyond SQL

Because YugabyteDB is a distributed SQL database, YSQL has a number of features that are not present in PostgreSQL, as summarized in the following table.

YSQL Feature	Description
Data distribution with HASH	Enables the use of HASH sort order, in addition to ASC and DESC for indexes
Tablespaces	Enables pinning of data in tables and table partitions to different geographic locations
Follower Reads	Enables more read IOPS with low latencies in YugabyteDB clusters