Introduction to PostgreSQL SQL Syntax (Compatibility and Extensions with Standard SQL)

Introduction

PostgreSQL is an open-source relational database management system that supports standard SQL syntax and offers many additional features and options.

Compatibility

PostgreSQL supports most of the standard SQL syntax, but there are some differences in how certain features are implemented. Some examples include:

  • Data Types: PostgreSQL supports many data types that are not available in all databases, such as bytea for binary data and inet for IP addresses.
  • Operators: PostgreSQL has its own set of operators, such as <> (not equal) instead of !=.
  • Functions: PostgreSQL supports many functions that are not available in all databases, such as now() to get the current timestamp.

Extensions

PostgreSQL also provides many additional features and options, for example:

  • Indexing: PostgreSQL supports various indexing types, including B-tree indexes and hash indexes.
  • Views: PostgreSQL supports views (views), which are virtual tables that can compute data.
  • Triggers: PostgreSQL supports triggers (triggers), programs that take action on specific events.
  • Stored Procedures: PostgreSQL supports stored procedures (stored procedures), programs that may contain multiple SQL statements.

Composite Expressions

PostgreSQL supports many composite expressions, for example:

  • JOIN: PostgreSQL supports inner joins (INNER JOIN) and outer joins (LEFT JOIN, RIGHT JOIN, FULL OUTER JOIN).
  • SUBQUERY: PostgreSQL supports subqueries (SUBQUERY).
  • CASE_statement: PostgreSQL supports CASE statements.

Common Functions

PostgreSQL provides many commonly used functions, for example:

  • NOW(): Gets the current time.
  • RANDOM(): Generates a random number.
  • CURRENT_DATE: Gets the current date.
  • CURRENT_TIME: Gets the current time.

Note: This article is an introductory overview and may not be comprehensive. For specific PostgreSQL issues, it is recommended to refer to PostgreSQL Official Documentation.