To delete duplicate rows in PostgreSQL using a self-join, you can use the DELETE statement along with a self-join condition. Here’s the syntax: DELETE FROM your_table a USING your_table b WHERE a.column_name = b.column_name AND a.ctid < b.ctid; where your_table is the actual name of your table, and column_name is the column that you want…

To find duplicate values in a PostgreSQL table, you can use the GROUP BY clause along with the HAVING clause. Here is the syntax: SELECT column_name, COUNT(column_name) AS count FROM your_table GROUP BY column_name HAVING COUNT(column_name) > 1; where your_table is the actual name of your table and column_name is the column for which you…

To select rows from one table that do not exist in another table in PostgreSQL, you can use the NOT EXISTS clause. SELECT * FROM table1 WHERE NOT EXISTS ( SELECT 1 FROM table2 WHERE table1.column_name = table2.column_name ); where table1 and table2 are the actual table names, and column_name is the column you want…

To revert to the original role of the logged in user, you can use the RESET ROLE statement. This will revert to the role of the logged-in user. Here is the syntax of using the RESET ROLE command: RESET ROLE; I’m currently logged in as user ‘postgres’ as shown in the below screenshot: Using the…

The is_superuser configuration setting or attribute determines whether a user has superuser privileges or not. Superusers have the highest level of access and control over a PostgreSQL database cluster, including the ability to perform critical administrative functions. The is_superuser setting is a boolean attribute associated with database roles (users). When a user is designated as…

You can change the current role within a database session in PostgreSQL database using SET ROLE statement . Changing the role allows you to temporarily assume the permissions and privileges associated with a different role, which can be useful for specific tasks or actions that require different access rights. This can be particularly helpful in…

You can use the session_user function to retrieve the name of the user that established the database session. Here’s how you can use the session_user function in SQL queries: SELECT session_user; When you execute this SQL query, it will return the name of the user that established the session. It could be same as currently…

The log_rotation_size parameter determines the size at which PostgreSQL’s log files (usually the log file generated by the pg_log system) will be rotated or switched to a new file. Rotating log files helps postgresql database engine to manage the log file size and prevent them from growing too large, which can be particularly useful for…

You can use the RANDOM() function to generate a random floating-point number between 0 and 1 in PostgreSQL database. Here’s the basic syntax for using the RANDOM() function: SELECT RANDOM(); This will return a random number in the range [0, 1), meaning it can be any decimal value between 0 (inclusive) and 1 (exclusive). If…

You can count the number of rows in a table in PostgreSQL using the SELECT COUNT(*) query. Here’s how you can do it: SELECT COUNT(*) FROM table_name; Replace table_name with the name of the table for which you want to count the rows. When you run this query, PostgreSQL will return a single value, which…