一、普通查询
select * from STU
select * from stu where ROWNUM<=3
select * from stu where stu_id like 'stu001%'
说明：通配符“%”代表一个或者多个字符，通配符“_”代表一个字符。
select STU_ID as 学号 from stu
二、联合查询
SELECt STU.STU_NAME, STU.STU_AGE, KC.KC_NAME FROM STU, KC WHERe STU.KC_NO = KC.KC_NO
SELECt STU.STU_NAME, STU.STU_AGE, KC.KC_NAME FROM STU INNER JOIN KC ON STU.KC_NO = KC.KC_NO ORDER BY STU.STU_ID
SELECt STU.STU_NAME, STU.STU_AGE, KC.KC_NAME FROM STU LEFT JOIN KC ON STU.KC_NO = KC.KC_NO ORDER BY STU.STU_ID
SELECt STU.STU_NAME, STU.STU_AGE, KC.KC_NAME FROM STU RIGHT JOIN KC ON STU.KC_NO = KC.KC_NO ORDER BY STU.STU_ID
SELECt STU.STU_NAME, STU.STU_AGE, KC.KC_NAME FROM STU FULL JOIN KC ON STU.KC_NO = KC.KC_NO ORDER BY STU.STU_ID
SELECt STU_NAME FROM STU UNIOn SELECt KC_NAME FROM KC
