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PostgreSQL

Introduction

Convention

  • [ ] - optional parts
  • { }, a | b - choose one alternative
  • ... - preceding element can be repeated
  • => - sql commands
  • $ - shell commands

Postgres uses client/server model - Server process - postgres program manages database files, accepts connections to the database from client applications, and performs database actions on behalf of the clients. - Client application - that wants to perform database opeartions. In case client/server are on different host TCP/IP is used. - To handle concurrent connections from the clients, the server "forks" a new process for each connection, and postgres main process hands all the responsibilities to this process for the client.

SQL Syntax

Lexical Structure

Keywords

  • Like SELECT, UPDATE that have a fixed meaning in SQL language.
  • Case-insensitive.

Identifier (also called anmes)

  • Like table name, column name.
  • Unquoted identifiers are case-insensitive (convention is to use lower case).

Naming convention for keyword, identifer

  • Start with a-z or _ and then can use letters, underscore, digits, dollar sign (to make SQL more portable avoid using dollar sign).
  • The max length is NAMEDATALEN-1 bytes (63 by default). Longer names would automatically be truncated. Can be adjusted by changing NAMEDATALEN in src/include/pg_config_manual.h.
Last update: November 21, 2023
Created: November 21, 2023