Mysql MAX和Count之间的减法运算
我想得到一个作者写的书的最大数量和每个作者写的书的数量之间的差异Mysql MAX和Count之间的减法运算,mysql,sql,Mysql,Sql,我想得到一个作者写的书的最大数量和每个作者写的书的数量之间的差异 SELECT count(book_name) contar, (MAX(C.qty) - count(book_name)) final FROM (select B.author_id, count(book_name) qty FROM author A ,BOOK B WHERE A.author_id = B.author_id GROUP BY b.author_id) C ,
SELECT count(book_name) contar, (MAX(C.qty) - count(book_name)) final
FROM (select B.author_id, count(book_name) qty
FROM author A ,BOOK B
WHERE A.author_id = B.author_id
GROUP BY b.author_id) C ,
author A,
BOOK B
WHERE A.author_id = B.author_id
AND B.author_id=C.Author_id
AND date_release BETWEEN NOW() - INTERVAL 20 YEAR AND NOW()
GROUP BY c.author_id
HAVING contar > 0
BOOKBOOK\u idauthor\u idBOOK\u namedate\u releaseauthorauthor\u nameauthor\u lastname日期--------+-------+--+
| contar | final | |
+--------+-------+--+
| 1 | -4 | |
| 2 | -3 | |
| 5 | 0 | |
| 1 | -4 | |
+--------+-------+--+
试试这个。我让每个数字等于一个变量，然后减去这些变量。但是，变量将显示为列
SELECT count(book_name) contar,
@max:=( MAX(C.qty) ),
@bookcount:=( count(book_name) ),
@final:= @max-@bookcount
FROM (select B.author_id,
count(book_name) qty
FROM author A , BOOK B
WHERE A.author_id = B.author_id
GROUP BY b.author_id) C ,
author A,
BOOK B
WHERE A.author_id = B.author_id
AND B.author_id = C.Author_id
AND date_release BETWEEN NOW() - INTERVAL 20 YEAR
AND NOW()
GROUP BY c.author_id
HAVING contar > 0
问题是，
MAX（C.qty）GROUP BY C.author\u id作者图书SELECT count(book_name) contar, (max_qty - count(book_name)) final
FROM (SELECT MAX(qty) AS max_qty
FROM (select count(book_name) qty
FROM BOOK B
GROUP BY b.author_id) t
) C
CROSS JOIN author A
JOIN book B ON A.author_id = B.author_id
WHERE date_release BETWEEN NOW() - INTERVAL 20 YEAR AND NOW()
GROUP BY A.author_id
而且没有必要让
拥有contar>0连接中连接