SELECT playerno
FROM 
    (SELECT playerno, sex
    FROM players
    WHERE playerno < 10) AS players10
WHERE sex=‘M‘;

SELECT playerno
FROM players
WHERE (sex, town) = 
    (SELECT sex,
         town
    FROM players
    WHERE playerno = 100);

SELECT playerno, name, town
FROM players
WHERE playerno IN 
    (SELECT playerno
    FROM players
    WHERE sex = ‘F‘);

SELECT playerno
FROM players
WHERE year(birth_date) = 
    (SELECT year(birth_date)
    FROM players
    WHERE playerno = 27)
        AND playerno <> 27; 

SELECT * FROM t_blog JOIN t_type ON t_blog.typeId=t_type.id;
SELECT * FROM t_blog,t_type WHERE t_blog.typeId=t_type.id;

SELECT * FROM t_blog LEFT JOIN t_type ON t_blog.typeId=t_type.id;