Postgres and Open Source Experts

The STRING_TO_ARRAY() function accepts a string as the first argument, splits it into array elements, and concatenates the array elements using a delimiter/separator.

ARRAY_CAT() is another very convenient function in Postgres that is used to concatenate two arrays. It accepts two arrays as arguments and retrieves a concatenated array.

In PostgreSQL, the WHERE clause allows us to filter the result set retrieved by the UPDATE, SELECT, or DELETE query. The WHERE clause filters the data based on a specific condition or several conditions.

In PostgreSQL, several syntaxes can be used to insert data into an array, such as using the ARRAY keyword with square brackets “[]” or curly braces enclosed within single quotes.

In PostgreSQL, the RENAME TO clause is used along with the ALTER USER or the ALTER ROLE statement to rename a user/role.

In PostgreSQL, bulk data can be inserted into a table using an INSERT INTO statement or COPY command. In Postgres, the COPY command allows us to load bulk data from one or more files.

To create a user in Postgres, specify the “CREATE USER” command followed by the user name, and after that, assign the privileges to the user using the “WITH” clause.

PostgreSQL allows us to concatenate a string with a number using a built-in “CONCAT()” function or a pipe concatenation operator “||”.

A Postgres user's attributes can be changed using the ALTER USER statement. Using the ALTER USER command, we can modify/alter the user's password, privileges, etc..

To find the logged-in users in Postgres, the “pg_stat_activity” view is used. While to find all Postgres users, a system table named "pg_user" is used.