mysql group_concat 和 group by 不工作

Question

I have the following two tables (simplified):

tblinvoices

id  dateCreated    

1   2020-01-02
2   2020-01-03
3   2020-01-03
4   2020-01-04

tblinvoicesLines

id invoiceId vatId vatAmount
1  4         7     35.50
2  4         8     15.75
3  4         7     11.50
3  5         7     10.05
4  6         7     11.04

I am trying to aggregate the vatAmount results in the output, like for this example:

invoiceId   listVatAmounts
4          47.00,15.75
5          10.05
6          11.04

I have the following mysql query:

select
tblInvoices.id as invoiceId,

(
select group_concat(vatAmount) from tblinvoicesLines
where tblinvoicesLines.invoiceId=tblInvoices.id
group by tblinvoicesLines.vatId
) as listVatAmounts

from tblInvoices
order by id desc
limit 10

I was hoping the group by tblinvoicesLines.vatId would group these values together, but mysql returns an error:

Subquery returns more than 1 row

What can I do to achieve the desired result? I want it to be achieved via a subquery.

Answer 1

You need to perform the sums by vatId first, and then you can list the vatAmount sums by invoiceId :

SELECT invoiceId, GROUP_CONCAT(sumVatAmounts) AS listVatAmounts
FROM (SELECT invoiceId, vatId, SUM(vatAmount) AS sumVatAmounts
      FROM tblinvoicesLines
      GROUP BY invoiceId, vatId) t
GROUP BY invoiceId

Output:

invoiceId   listVatAmounts
4           47.00,15.75
5           10.05
6           11.04

If you need to include values from tblInvoices , you can just JOIN that table to the above query as a derived table:

SELECT i.id AS invoiceId, i.dateCreated, GROUP_CONCAT(t.sumVatAmounts) AS listVatAmounts
FROM tblInvoices i
LEFT JOIN (SELECT invoiceId, vatId, SUM(vatAmount) AS sumVatAmounts
           FROM tblinvoicesLines
           GROUP BY invoiceId, vatId) t ON t.invoiceId = i.id
GROUP BY i.id, i.dateCreated

Or if you really must use a subquery:

SELECT i.id AS invoiceId,
       (SELECT GROUP_CONCAT(sumVatAmounts)
        FROM (SELECT invoiceId, vatId, SUM(vatAmount) AS sumVatAmounts
              FROM tblinvoicesLines
              GROUP BY invoiceId, vatId) t
        WHERE t.invoiceId = i.id) AS listVatAmounts
FROM tblInvoices i

Demo on dbfiddle

Answer 2

You can also do it with one SELECT like this:

SELECT  invoiceId, CONCAT(
    SUM(IF(vatId=7,vatAmount,0))
    ,if( SUM(IF(vatId=8,vatAmount,0)) >0
        , CONCAT(',',SUM(IF(vatId=8,vatAmount,0)))
        ,'')
    ) AS listVatAmounts
FROM invoiceId
GROUP BY invoiceId;

OR with subquery and for all invoiceIds

SELECT
    invoiceId,
    GROUP_CONCAT(vatAmount ORDER BY vatId SEPARATOR ', ') AS listVatAmounts
FROM (
    SELECT id, invoiceId, vatId, SUM(vatAmount) as vatAmount
    FROM invoiceId
    GROUP BY invoiceId,vatId
    ) grp
GROUP BY invoiceId
ORDER BY id;

Sample

MariaDB [bernd]> SELECT  invoiceId, CONCAT(
    ->     SUM(IF(vatId=7,vatAmount,0))
    ->     ,if( SUM(IF(vatId=8,vatAmount,0)) >0
    ->         , CONCAT(',',SUM(IF(vatId=8,vatAmount,0)))
    ->         ,'')
    ->     ) AS listVatAmounts
    -> FROM invoiceId
    -> GROUP BY invoiceId;
+-----------+----------------+
| invoiceId | listVatAmounts |
+-----------+----------------+
|         4 | 47.00,15.75    |
|         5 | 10.05          |
|         6 | 11.04          |
+-----------+----------------+
3 rows in set (0.01 sec)

MariaDB [bernd]>

Sample 2

MariaDB [bernd]> SELECT
    ->     invoiceId,
    ->     GROUP_CONCAT(vatAmount ORDER BY vatId SEPARATOR ', ') AS listVatAmounts
    -> FROM (
    ->     SELECT id, invoiceId, vatId, SUM(vatAmount) as vatAmount
    ->     FROM invoiceId
    ->     GROUP BY invoiceId,vatId
    ->     ) grp
    -> GROUP BY invoiceId
    -> ORDER BY id;
+-----------+----------------+
| invoiceId | listVatAmounts |
+-----------+----------------+
|         4 | 47.00, 15.75   |
|         5 | 10.05          |
|         6 | 11.04          |
+-----------+----------------+
3 rows in set (0.00 sec)

MariaDB [bernd]>

Answer 3

What Ive done is the following:

select
@invoiceId:= tblInvoices.id as invoiceId,

(
select group_concat(vatAmount)
from
(
select sum(vatAmount) as vatAmount
from tblinvoicesLines
where tblinvoicesLines.invoiceId=@invoiceId
group by tblinvoicesLines.vatId
) t
)

as listVatAmounts

from tblInvoices
order by id desc
limit 10

But the performance is not very well. It does it however in one subquery