SQL allows a rudimentary form of patterns in which two characters have special meaning: underscore (_) stands for any one character and percent-sign (%) stands for any string of $0$ or more characters. In addition, the programmer may define any character, say e, to be the escape character, so e preceding an e preceding -, %, or another e gives the character that follows its literal meaning. Show how to express any SQL pattern as a regular expression, given that we know which character is the escape character.
