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  To create a read-only user in PostgreSQL, you can follow these steps: Connect to your PostgreSQL database using an account with administrative privileges. You can use a tool like psql or a graphical client. Once connected, run the following SQL command to create a new user: sql CREATE USER your_username WITH PASSWORD 'your_password' ; Replace your_username with the desired username for the read-only user, and your_password with the desired password. Grant the necessary permissions to the user. In this case, you want to provide read-only access, so you can grant the SELECT privilege on the desired tables or schemas. For example, to grant SELECT access on all tables in a specific schema: sql GRANT SELECT ON ALL TABLES IN SCHEMA your_schema TO your_username; Replace your_schema with the name of the schema containing the tables you want to provide read-only access to. If you want to grant SELECT access on specific tables, you can use the following command for each

  Photo by olia danilevich: https://www.pexels.com/photo/little-girls-lying-on-green-grass-field-4982457/ To check if a row exists in PostgreSQL, you can use the EXISTS keyword in conjunction with a subquery. Here's an example: sql SELECT EXISTS ( SELECT 1 FROM your_table WHERE your_condition) AS row_exists; Replace your_table with the name of your table and your_condition with the condition that specifies the row you want to check for existence. The subquery SELECT 1 FROM your_table WHERE your_condition will return a single row with the value 1 if the row exists, or no rows if it doesn't exist. The outer query SELECT EXISTS (...) AS row_exists wraps the subquery and uses the EXISTS function to return a boolean value indicating whether the subquery returned any rows. The result will be true if the row exists and false if it doesn't. You can execute this query using your preferred method of accessing the PostgreSQL database, such as through a programming langua

  Photo by Irina Iriser: https://www.pexels.com/photo/tilt-shift-lens-photo-of-blue-flowers-673857/ In PostgreSQL, the CASE expression allows you to add conditional logic to your queries. You can use the CASE expression to perform different operations based on a set of conditions. Here's the syntax for using the CASE expression in PostgreSQL: sql CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... ELSE default_result END Here's an example of how to use the CASE expression in a SELECT statement: sql SELECT first_name, last_name, CASE WHEN age < 18 THEN 'Minor' WHEN age BETWEEN 18 AND 65 THEN 'Adult' ELSE 'Senior' END AS age_group FROM employees;