Glossary
Check constraint
Type of constraint It allows you to specify that the value in a certain column or a group of columns must satisfy a Boolean (truth-value) expression.
Column
An attribute with a certain name and data type in a table or view.
Constraint
A restriction on the values of data allowed within a table, or in attributes of a domain.
Source: PostgreSQL glossary
Database
A database is a structure used to organize and store data. Specifically in PostgreSQL, a database is named collection of local SQL objects.
Data type
A data type is the kind of data that can be stored in a table column or returned by a function. It specifies the format and limitations of the data, such as whether it’s a number, text, date, or something more complex like a JSON object. For example, the data type ìnteger is used for whole, and character varying is used for variable-length character strings.
Extension
A software add-on package that can be installed on an instance to get extra features.
Source: PostgreSQL glossary
Foreign Key
A type of constraint defined on one or more columns in a table which requires the value(s) in those columns to identify zero or one row in another (or, infrequently, the same) table.
Source: PostgreSQL glossary
Function
Code that you can run within a database query. It can take inputs, return outputs, and always runs within one transaction. You can call a function as a part of a query, for example via SELECT. Some functions can return multiple rows of data, and these are known as set-returning functions.
Functions can also be used for triggers to invoke.
Index
A SQL object that contains data derived from a table or materialized view, allowing for fast retrieval and access of the original data.
Primary Key
A constraint that enforces values to be unique and NOT NULL. A primary key is used to reliably identify and distinguish between each individual record in a table and there can be only one primary key per table.
Schema
A schema is a namespace for SQL objects, which all reside in the same database. Each SQL object must reside in exactly one schema.
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More generically, the term schema is used to mean all data descriptions (table definitions, constraints, comments, etc.) for a given database or subset thereof.
Source: PostgreSQL glossary
Session
A state that allows a client and a backend to interact, communicating over a connection.
Source: PostgreSQL glossary
SQL Object
In PostgreSQL, an “sql object” refers to anything you can create using a CREATE command, like tables, functions, or data types. Most of these objects are tied to a specific database and live within schemas, which are like folders that help organize them. For example, tables and functions in the same schema must have unique names. Some objects, like extensions, don’t live in schemas but still need unique names within their database. Additionally, there are global objects like roles, tablespaces, and databases that exist outside any single database and must have unique names across the entire database instance.
Table
A collection of rows that share the same structure, where each row has the same set of columns in the same order and has the same name and data type across all rows.
Transaction
A combination of commands that all succeed or all fail as a single unit. If a system failure occurs during the execution of a transaction, no partial results are visible after recovery. Transaction effects are not visible to other sessions until the transaction is complete, and possibly even later, depending on the isolation level.
Unique constraint
Type of constraint that ensures that the data contained in a column, or a group of columns, is unique among all the rows in the table.
Trigger
A function which can be defined to execute whenever a certain operation (INSERT, UPDATE, DELETE, TRUNCATE) is applied to a relation. A trigger executes within the same transaction as the statement which invoked it, and if the function fails, then the invoking statement also fails.
Source: PostgreSQL glossary