How many users participated in the mental health survey for 2014?
mental health survey for 2014 refers to SurveyID = 2014
SELECT COUNT(DISTINCT T1.UserID) FROM Answer AS T1 INNER JOIN Survey AS T2 ON T1.SurveyID = T2.SurveyID WHERE T2.Description = 'mental health survey for 2014'
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)
);
