[ ]- 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.
UPDATEthat have a fixed meaning in SQL language.
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
_and then can use letters, underscore, digits, dollar sign (to make SQL more portable avoid using dollar sign).
- The max length is
NAMEDATALEN-1bytes (63 by default). Longer names would automatically be truncated. Can be adjusted by changing
Created: November 21, 2023