Postgres and Open Source Experts

PostgreSQL provides a built-in function named TO_DATE() that assists us in converting a string into a date. The TO_DATE() function retrieves a date value in “YYYY-MM-DD” format.

In Postgres, the CURRENT_TIMESTAMP retrieves the date and time along with the time zone, while the LOCALTIMESTAMP function retrieves the date and time without the time zone.

In PostgreSQL, the TO_TIMESTAMP() is a built-in function that accepts a string and a format and converts the given string to a TIMESTAMP based on the specified format.

In PostgreSQL, the INTERSECT operator combines the result set of at least two queries. The INTERSECT operator retrieves only common records from the targeted tables.

In PostgreSQL, there are multiple ways to export a table into a CSV file, such as the COPY statement or the \COPY command.

PostgreSQL provides a built-in function named UNNEST() that accepts an array as an argument and expands the given array into a set of rows.

Sometimes we have to store the unique records in a table, such as an email address, employee id, etc. To achieve this purpose, the “UNIQUE” constraint is used in PostgreSQL. The UNIQUE constraint allows us to store the unique rows/records in a table.

This post will explain the working of the UNIQUE constraint through practical examples. So, let’s begin.

How Does UNIQUE Constraint Work in PostgreSQL?

Each time when you …

PostgreSQL offers a CAST operator that takes an expression and a data type and converts the given expression into the specified data type.

The DROP command throws an error if a table to be dropped doesn’t exist while “DROP IF EXISTS” shows a notice instead of throwing an error.

In Postgres, the SELECT DISTINCT clause fetches only unique values from a result set returned by a query. It retains only one row from a set of duplicated rows.