PostgreSQL - problems

• PostgreSQL - Create or replace view
• PostgreSQL - Create table if not exists
• PostgreSQL - Create table with FOREIGN KEY
• PostgreSQL - Create table with JSON field
• PostgreSQL - Create view if not exist
• PostgreSQL - Drop table if exists
• PostgreSQL - Drop view if exists
• PostgreSQL - GROUP BY multiple columns
• PostgreSQL - Insert JSON type value to the table
• PostgreSQL - Insert NULL values
• PostgreSQL - UPDATE query with LIMIT
• PostgreSQL - Update all rows
• PostgreSQL - Update multiple rows at once
• PostgreSQL - add FOREIGN KEY to existing table
• PostgreSQL - add column to existing table
• PostgreSQL - average value for grouped rows
• PostgreSQL - calculate average of column values and display the result with no decimals
• PostgreSQL - check version from command line
• PostgreSQL - check version using SQL
• PostgreSQL - concatenate multiple columns into one
• PostgreSQL - concatenate multiple rows into one field
• PostgreSQL - count distinct values
• PostgreSQL - count duplicated rows
• PostgreSQL - count rows with NULL values
• PostgreSQL - delete all duplicated rows except one
• PostgreSQL - delete row where column is empty string (blank)
• PostgreSQL - delete row where column is null
• PostgreSQL - duplicate table
• PostgreSQL - find duplicated values
• PostgreSQL - find duplicated values in multiple columns
• PostgreSQL - find first row
• PostgreSQL - find row with null value in column
• PostgreSQL - find row with null value in one of many columns
• PostgreSQL - find rows where column is empty string (blank)
• PostgreSQL - get row position with SELECT query
• PostgreSQL - make column values unique
• PostgreSQL - max value for grouped rows
• PostgreSQL - minimum value for grouped rows
• PostgreSQL - search for NULL values in multiple columns
• PostgreSQL - select first N rows
• PostgreSQL - select from view
• PostgreSQL - select last N rows
• PostgreSQL - select last row
• PostgreSQL - select rows with max value of column
• PostgreSQL - sort in ascending or descending order
• PostgreSQL - sum value for grouped rows