Postgres and Open Source Experts

In PostgreSQL, creating a table from a CSV file means importing a CSV file into the Postgres table. For this, execute the COPY command to create a Postgres table via the CSV file.

PostgreSQL provides a built-in function named ARRAY_CAT() and a concatenation operator “||” that assists us in concatenating multiple arrays into a single array.

Execute the “ALTER USER” or “ALTER ROLE” command, followed by the default user name and the PASSWORD attribute to set the default user password in PostgreSQL.

In PostgreSQL, the DATE_TRUNC() function is a convenient way for truncating/rounding the timestamps to the desired level of precision.

Sometimes a “Permission Denied” error occurs while importing a CSV file into a Postgres table. To fix this error, you need to change the file reading permissions.

In Postgres, the DEFAULT keyword is used with the help of CREATE TABLE or ALTER TABLE statement to set a default value to a column.

To extract a year from a date, the built-in EXTRACT() and DATE_PART() functions are used in Postgres. To do so, pass the “YEAR" and the timestamp as arguments to any of these functions.

In PostgreSQL, the DELETE CASCADE feature allows us to delete the records associated with some other tables (via foreign key constraints).

In Postgres, the EXTRACT(), DATE_TRUNC(), and DATE_PART() functions are used to extract the month from a date field and then use the GROUP BY clause to group the results by month.

In PostgreSQL, the DATE_PART() function, INTERVAL, and the minus “-” operator is used to subtract a single or multiple days from a particular date.