创建一个学生表，插入10条数据

CREATE TABLE student (id int, name varchar(20), score integer);INSERT INTO student VALUES (1, 'jack', 90);INSERT INTO student VALUES (2, 'tom', 85);INSERT INTO student VALUES (3, 'allen', 79);INSERT INTO student VALUES (4, 'michael', 95);INSERT INTO student VALUES (5, 'steven', 65);INSERT INTO student VALUES (6, 'kevin', 100);INSERT INTO student VALUES (7, 'kate', 60);INSERT INTO student VALUES (8, 'david', 55);INSERT INTO student VALUES (9, 'kelly', 95);INSERT INTO student VALUES (10, 'bale', 99);

查询分数小于80分的学生，显示row_number

SELECT  @curRow := @curRow + 1 AS row_num,s.id,s.name,s.scoreFROM    student sJOIN    (SELECT @curRow := 0) rWHERE   s.score < 80;