What is the average number of respondents per survey between 2014 and 2019?
respondents and 'users' are synonyms; average number = avg(count(userID(SurveyID = 2014)), count(userID(SurveyID = 2019)))
SELECT CAST(COUNT(SurveyID) AS REAL) / 5 FROM Answer WHERE SurveyID BETWEEN 2014 AND 2019
CREATE TABLE Question
(
    questiontext TEXT,
    questionid   INTEGER
        constraint Question_pk
            primary key
);
CREATE TABLE Survey
(
    SurveyID    INTEGER
        constraint Survey_pk
            primary key,
    Description TEXT
);
CREATE TABLE IF NOT EXISTS "Answer"
(
    AnswerText TEXT,
    SurveyID   INTEGER
        constraint Answer_Survey_SurveyID_fk
            references Survey,
    UserID     INTEGER,
    QuestionID INTEGER
        constraint Answer_Question_questionid_fk
            references Question,
    constraint Answer_pk
        primary key (UserID, QuestionID)
);
