Postgres and Open Source Experts

The ENUM_FIRST() is a built-in function in Postgres that retrieves the first value of the enum specified by the parameter.

The JSON_BUILD_OBJECT() function is used to create and retrieve a JSON object from a variadic parameter list of key-value pairs.

The JSON_BUILD_ARRAY() is a built-in JSON function that creates and retrieves a JSON array of different types from a variadic parameter list.

The array_to_json() is a built-in JSON function that accepts a SQL array as an argument and converts it into a JSON array.

In PostgreSQL, various methods are used to exit the Postgres command line utility, such as the “\q” or “\quit” commands, and “CTRL + C”, “CTRL + D”, or “CTRL + Z” shortcut keys.

To include multiple PostgreSQL databases in Docker container, continuously run the “CREATE DATABASE <database-name>” command with different database names.

In PostgreSQL, the “table inheritance” allows us to create a hierarchy of tables, where one table(child) can inherit the structure and properties of another (parent) table.

In PostgreSQL, the “UNIQUE” keyword is used with the CREATE TABLE or ALTER TABLE commands to add a unique constraint on single/multiple columns of a new or an already existing Postgres table.

The DENSE_RANK() function assigns a rank to each row of a partition based on the specified sorting order. It starts ranking from 1 for the first row and increases the rank for each subsequent row.

PostgreSQL supports various commands to create a database from the command line, including “createdb” and “CREATE DATABASE”.