2.2的答案 SELECT TIMESTAMPDIFF(DAY,MIN(t.HIREDATE),MAX(t.HIREDATE)) `相差天数`, TIMESTAMPDIFF(MONTH,MIN(t.HIREDATE),MAX(t.HIREDATE)) `相差月数`, TIMESTAMPDIFF(YEAR,MIN(t.HIREDATE),MAX(t.HIREDATE)) `相差年数` FROM 表名 t ;
2.1答案 SET @c := (SELECT COUNT(0) FROM 表名) ; SET @c1 :=FLOOR(@c/2); SET @c2 :=CEIL(@c/2) ; SELECT AVG(t.数字) FROM ( SELECT t.数字,@r:=@r+1 r FROM ( SELECT id,@r:=0 FROM 表名 WHERE DNAME='Research Institute' ORDER BY id ) t) t WHERE t.r BETWEEN @c1 AND @c2;
SELECT
TIMESTAMPDIFF(DAY,MIN(t.HIREDATE),MAX(t.HIREDATE)) `相差天数`,
TIMESTAMPDIFF(MONTH,MIN(t.HIREDATE),MAX(t.HIREDATE)) `相差月数`,
TIMESTAMPDIFF(YEAR,MIN(t.HIREDATE),MAX(t.HIREDATE)) `相差年数`
FROM 表名 t ;
SET @c := (SELECT COUNT(0) FROM 表名) ;
SET @c1 :=FLOOR(@c/2);
SET @c2 :=CEIL(@c/2) ;
SELECT AVG(t.数字) FROM (
SELECT t.数字,@r:=@r+1 r FROM (
SELECT id,@r:=0 FROM 表名 WHERE DNAME='Research Institute' ORDER BY id ) t) t WHERE t.r BETWEEN @c1 AND @c2;