Postgres and Open Source Experts

To make the conditional selection in PostgreSQL, the CASE expression must be used within the SELECT statement.

The “-” operator, DATE_PART(), EXTRACT(), and AGE() functions can be used in PostgreSQL to calculate the difference between various DateTime values.

In Ubuntu, “/etc/init.d/postgresql” and the “systemctl” commands are used with the “start” or “stop” option to activate or deactivate the Postgres server, respectively.

In PostgreSQL, a composite primary key can be defined as a combination of two or more columns that guarantees the uniqueness of a record.

In PostgreSQL, the “psql command not found” error arises if Postgres is not installed or the path for Postgres tools is not set on your system.

In PostgreSQL, the pg_sleep() function accepts the fractional seconds as arguments and delays the execution until the specified seconds pass

In PostgreSQL, the TRIM_ARRAY() function trimmed the specified number of elements from the end of the given array and return a newly updated array.

PostgreSQL uses the INNER JOIN to get matching results from two or more tables based on the defined join conditions.

In Postgres, there is no such function that directly retrieves yesterday’s date. However, any Postgres function that returns today’s date can be used with the “-” operator to get yesterday’s date.

To uninstall PostgreSQL from CentOS, execute the “yum remove postgresql-server postgresql-contrib” command.