我的查询很简单 - 它每月/每年抓取银行及其交易金额:
select bank_name,
sum(payment_sum),
CONCAT(MONTH(payment_due_date), '/', YEAR(payment_due_date)) as month_year
from bank
join finance
on bank.bank_id = finance.bank_id
group by bank_name, month_year
返回:
如何将行值(month_year)转换为列,然后pay_sum也转发到相应的month_year生成列?
我正在寻找一种方法来按月找到每家银行的付款总额。
我查看了this主题,但我的需求似乎有所不同。
答案 0 :(得分:2)
不幸的是,MySQL没有将行转换为列的PIVOT函数,因此您需要使用带有CASE表达式的聚合函数。
如果列数有限或已知,则查询的基本语法为:
select bank_name,
sum(case when month_year ='10/2011' then payment_sum else 0 end) `10/2011`,
sum(case when month_year ='11/2011' then payment_sum else 0 end) `11/2011`,
sum(case when month_year ='12/2011' then payment_sum else 0 end) `12/2011`
from
(
select bank_name,
payment_sum,
CONCAT(MONTH(payment_due_date), '/', YEAR(payment_due_date)) as month_year
from bank
join finance
on bank.bank_id = finance.bank_id
) d
group by bank_name;
但是对于你的情况,听起来你会有一个未知数量的日期,所以你可能需要使用预准备语句来创建动态sql:
SET @sql = NULL;
SELECT
GROUP_CONCAT(DISTINCT
CONCAT(
'sum(case when month_year = ''',
CONCAT(MONTH(payment_due_date), '/', YEAR(payment_due_date)),
''' then payment_sum end) AS `',
CONCAT(MONTH(payment_due_date), '/', YEAR(payment_due_date)), '`'
)
) INTO @sql
from finance;
SET @sql
= CONCAT('SELECT bank_name, ', @sql, '
from
(
select bank_name,
payment_sum,
CONCAT(MONTH(payment_due_date), ''/'', YEAR(payment_due_date)) as month_year
from bank
join finance
on bank.bank_id = finance.bank_id
) d
group by bank_name;');
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;