Experts in Postgres and Open Source Infrastructure

Postgres provides an ARRAY_APPEND() function that is used to append/add elements at the end of the array. It accepts two parameters: an array and an element to be appended.

To get the first non-null value in Postgres, an inbuilt function named COALESCE() is used. It accepts the “n” number of arguments and retrieves the first non-null value.

In PostgreSQL, the OFFSET clause is used to skip some records before returning the result set of a query. By default, the OFFSET clause skipped the records from the top.

In PostgreSQL, the EXCEPT operator is used to compare multiple tables. It executes two SELECT queries and retrieves only those records that are not available in the second SELECT query.

In Postgres, the NOW() function retrieves the current date and time along with the time zone(based on the database server’s setting).

The Postgres LENGTH() function accepts a string as an argument and calculates the total number of characters in that particular string.

PostgreSQL provides a pg_relation_size() function to get the size of a particular table. The “pg_size_pretty()” function is used to get the table’s size in a human-readable format like KBs, MBs.

To rename a database in Postgres, specify an ALTER DATABASE command, followed by the database’s old name, and after that, specify the RENAME TO clause followed by the database’s new/modified name.

CURRENT_DATE is one of the Postgres built-in date functions that retrieve the current/today’s date. It doesn’t take any argument.

PostgreSQL offers a GRANT statement that is used to assign privileges to the database objects. In Postgres, you can grant all privileges to a user via the "GRANT ALL" statement.