13518219792
有点复杂，在你基础上加了条有奇数的数据
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创建表，插入数据：
create table test
(cat_id int,
price int);
insert into test values (101,90);
insert into test values (101,99);
insert into test values (102,98);
insert into test values (103,96);
insert into test values (102,95);
insert into test values (102,94);
insert into test values (102,93);
insert into test values (103,99);
insert into test values (103,98);
insert into test values (103,97);
insert into test values (104,96);
insert into test values (104,95);
insert into test values (105,97);
insert into test values (105,96);
insert into test values (105,95);
执行：
SELECT
t1.cat_id,
round(avg(t1.price), 1) price
FROM
(
SELECT
*
FROM
(
SELECT
t.cat_id,
t.price,
count(*) AS rank
FROM
test t
LEFT OUTER JOIN test r ON t.cat_id = r.cat_id
AND t.price = r.price
GROUP BY
t.cat_id,
t.price
ORDER BY
t.cat_id,
t.price DESC
) s
) t1,
(
SELECT DISTINCT
a.cat_id,
round(a.maxrank / 2) rank
FROM
(
SELECT
cat_id,
max(rank) maxrank,
MOD (max(rank), 2) modrank
FROM
(
SELECT
*
FROM
(
SELECT
t.cat_id,
t.price,
count(*) AS rank
FROM
test t
LEFT OUTER JOIN test r ON t.cat_id = r.cat_id
AND t.price = r.price
GROUP BY
t.cat_id,
t.price
ORDER BY
t.cat_id,
t.price DESC
) s
) t1
GROUP BY
cat_id
) a,
(
SELECT
*
FROM
(
SELECT
t.cat_id,
t.price,
count(*) AS rank
FROM
test t
LEFT OUTER JOIN test r ON t.cat_id = r.cat_id
AND t.price = r.price
GROUP BY
t.cat_id,
t.price
ORDER BY
t.cat_id,
t.price DESC
) s
) b
WHERE
a.cat_id = b.cat_id
AND a.modrank = 0
UNION ALL
SELECT DISTINCT
a.cat_id,
round(a.maxrank / 2) + 1 rank
FROM
(
SELECT
cat_id,
max(rank) maxrank,
MOD (max(rank), 2) modrank
FROM
(
SELECT
*
FROM
(
SELECT
t.cat_id,
t.price,
count(*) AS rank
FROM
test t
LEFT OUTER JOIN test r ON t.cat_id = r.cat_id
AND t.price = r.price
GROUP BY
t.cat_id,
t.price
ORDER BY
t.cat_id,
t.price DESC
) s
) t1
GROUP BY
cat_id
) a,
(
SELECT
*
FROM
(
SELECT
t.cat_id,
t.price,
count(*) AS rank
FROM
test t
LEFT OUTER JOIN test r ON t.cat_id = r.cat_id
AND t.price = r.price
GROUP BY
t.cat_id,
t.price
ORDER BY
t.cat_id,
t.price DESC
) s
) b
WHERE
a.cat_id = b.cat_id
AND a.modrank = 0
UNION ALL
SELECT DISTINCT
a.cat_id,
round(a.maxrank / 2) rank
FROM
(
SELECT
cat_id,
max(rank) maxrank,
MOD (max(rank), 2) modrank
FROM
(
SELECT
*
FROM
(
SELECT
t.cat_id,
t.price,
count(*) AS rank
FROM
test t
LEFT OUTER JOIN test r ON t.cat_id = r.cat_id
AND t.price = r.price
GROUP BY
t.cat_id,
t.price
ORDER BY
t.cat_id,
t.price DESC
) s
) t1
GROUP BY
cat_id
) a,
(
SELECT
*
FROM
(
SELECT
t.cat_id,
t.price,
count(*) AS rank
FROM
test t
LEFT OUTER JOIN test r ON t.cat_id = r.cat_id
AND t.price = r.price
GROUP BY
t.cat_id,
t.price
ORDER BY
t.cat_id,
t.price DESC
) s
) b
WHERE
a.cat_id = b.cat_id
AND a.modrank = 1
) t2
WHERE
t1.cat_id = t2.cat_id
AND t1.rank = t2.rank
GROUP BY
t1.cat_id
结果：
其中：
select * from (
select t.cat_id,t.price,count(*) as rank from test t
LEFT OUTER JOIN test r
on t.cat_id = r.cat_id
and t.price=r.price
group by t.cat_id,t.price
order by t.cat_id, t.price desc
) s
这条是主语句，主要是按照大小给出一个排名，然后根据中位数的公式，偶数的话，取最中间两个的平均数，奇数取最中间的数。自己研究一下吧。
改过了
把数取出：“第”和“节”两个字占4个字符
select substring(chaptername,3,len(chaptername)-4) from chapter
如果更新到order字段：
update chapter set order=convert(smallint,substring(chaptername,3,len(chaptername)-4))
MySQL的AVG函数是用来求出各种记录中的字段的平均值。
MySQL中语句如下：
update Table1set avg_price=(select avg(price) from Table2
where Table2=.ID=Table1.TID)
扩展资料
在使用数据库进行数据筛选时查询时，经常会用到一些聚合函数，如 count（），sum（），max（），min（），avg（）
聚合函数会把NULL排除在外，但Count（*）例外，并不会排除NULL；
AVG() 函数
AVG() 函数返回数值列的平均值。
SQL AVG() 语法
SELECT AVG(column_name) FROM table_name
sum为求平均值函数，将要求总和值的列sum(列名)
avg为求平均值函数，将要求平均值的列avg(列名)
nvl为如果未空则置空值为其他数据的函数，nvl(为空的列,将空值置成的其他值)
round为四舍五入函数，round(列名,保留小数位数)
