Postgres and Open Source Experts

In Postgres, a variable is declared with a particular data type, such as INTEGER, TEXT, DATE, etc. To declare a variable, use the “DECLARE var_name data_type:= expression;” syntax.

In PostgreSQL, comparison operators like greater than “>” and greater than or equal to “>=” can be used with the “CURRENT_DATE” function to get a date greater than or equal to today.

To copy a table from one database to another, open CMD as an administrator, and run the "pg_dump -U user –t table source_db | psql -U user target_db" command.

To install pgAdmin on Ubuntu, add the public key using Curl, add the pgAdmin repository using sudo, and execute the “sudo apt install pgAdmin4” command.

Execute the “sudo systemctl status postgresql” command to check the PostgreSQL service status on your Linux (Ubuntu) operating system.

Run the “\s” command from psql to get query history. To check the query history using pgAdmin, open the “query tool” and navigate to the “Query History” tab.

Postgres offers different built-in array functions that are used with the UPDATE command to modify an array, such as ARRAY_PREPEND(), ARRAY_REMOVE(), ARRAY_CAT(), etc.

In PostgreSQL, the INNER JOIN is used to get the matching results from two or more tables based on a specific join condition.

In PostgreSQL, built-in functions like pg_relation_size(), pg_database_size(), pg_size_pretty(), etc. are used to get the size of the table or database.

In Postgres, the VERSION(), CURRENT_DATABASE(), CURRENT_SCHEMA, and CURRENT_USER, functions are used to get the current version, database, schema, and user.