The PostgreSQL SUBSTRING() function is used to extract or return a substring from a string. The function accepts three arguments: the string to be searched, the start position, and the length of the substring. If no length is specified, the function will return the remainder of the string starting from the specified position.The PostgreSQL SUBSTRING() function is used to extract or return a substring from a string. The function takes three arguments: the string to extract from, the start position, and the length of the substring. If the start position is negative, it is counted from the end of the string. If the length is omitted, it defaults to 1.The PostgreSQL SUBSTRING() function is used to extract or return a part of a string. The function takes three parameters: the string to extract from, the starting position, and the number of characters to extract. The starting position is zero-based, so the first character in the string is at position 0. If the starting position is negative, it is counted from the end of the string. For example, to extract the last five characters from a string, you would use a starting position of -5.The PostgreSQL SUBSTRING() function extracts a substring from a string. The function starts the extraction at the character at the specified position and extracts the specified number of characters. If no length is specified, it extracts from the start position to the end of the string.