I am calculating the length of a sentence using Length (scalar function), then I also used that keyword in the sentence, but I am having an error for all the queries below: Error: Missing right parenthesis. 1-SELECT LENGTH('This sentence's length will be calculated') "Length of characters" FROM dual; 2- SELECT LENGTH('This sentence's 'length' will be calculated') "Length of characters" FROM dual; 3- SELECT LENGTH('This sentence's "length" will be calculated') "Length of characters" FROM dual; 4-SELECT LENGTH('This sentence's "\length\" will be calculated') "Length of characters" FROM dual; 5- SELECT LENGTH('This sentence's '\length\' will be calculated') "Length of characters" FROM dual; What should be the correct way to write this query? Thanks in advance