Forgive me if my German is rusty but I believe what you are trying to do is group by day of week correct? I don't know what database you are using so I will demonstrate in MySQL:
It looks like you have your layout decided upon so I will focus on the functional data queries in SQL. Based on your description, I am assuming a reasonable DDL. I hope you don't mind the English translation.
First our offer (angebot) table:
CREATE TABLE
offer
(
`id` bigint AUTO_INCREMENT,
`created` DATETIME ,
`from` VARCHAR(64) ,
`item` VARCHAR(64) ,
`amount` DECIMAL(8,2) ,
PRIMARY KEY (id)
);
Now here is a detail query on the table by day number (Tagesnummer). This one is for last month (Feb-2014)
SELECT
DAYOFWEEK(created) AS `tag_num`,
DAYNAME(created) AS `tag` ,
`created` ,
`from` ,
`item` ,
`amount`
FROM
`offer`
WHERE
`created` >= '2014-02-01'
AND `created` < '2014-03-01'
ORDER BY
DAYOFWEEK(created)
Example Output:
+---------+-----------+---------------------+-------------------+---------+--------+
| tag_num | tag | created | from | item | amount |
+---------+-----------+---------------------+-------------------+---------+--------+
| 1 | Sunday | 2014-02-23 13:23:10 | Ivor Quinn | B6C 5J9 | 91.12 |
| 1 | Sunday | 2014-02-23 05:21:33 | Ray Robbins | T2P 4T2 | 13.58 |
| 1 | Sunday | 2014-02-23 16:31:47 | Craig Orr | C2R 1I8 | 59.48 |
| 1 | Sunday | 2014-02-23 13:23:10 | Ivor Quinn | B6C 5J9 | 91.12 |
| 1 | Sunday | 2014-02-23 05:21:33 | Ray Robbins | T2P 4T2 | 13.58 |
| 1 | Sunday | 2014-02-23 16:31:47 | Craig Orr | C2R 1I8 | 59.48 |
| 2 | Monday | 2014-02-10 05:50:36 | Dale Estes | H9V 2L3 | 63.03 |
| 2 | Monday | 2014-02-24 06:45:23 | Damian Vincent | T8T 6E4 | 5.02 |
| 2 | Monday | 2014-02-10 05:50:36 | Dale Estes | H9V 2L3 | 63.03 |
| 2 | Monday | 2014-02-24 06:45:23 | Damian Vincent | T8T 6E4 | 5.02 |
| 3 | Tuesday | 2014-02-11 14:20:17 | Oscar Trevino | F2L 0T3 | 60.22 |
| 3 | Tuesday | 2014-02-11 05:45:39 | Hilel Cline | N4M 3V2 | 40.45 |
etc...
Here is a summary total of offer amounts by day for Feb-2014:
SELECT
DAYOFWEEK(created) AS `tag_num`,
DAYNAME(created) AS `tag` ,
SUM(`amount`)
FROM
`offer`
WHERE
`created` >= '2014-02-01'
AND `created` < '2014-03-01'
GROUP BY
DAYOFWEEK(created)
Example output:
+---------+-----------+---------------+
| tag_num | tag | SUM(`amount`) |
+---------+-----------+---------------+
| 1 | Sunday | 328.36 |
| 2 | Monday | 136.10 |
| 3 | Tuesday | 141.12 |
| 4 | Wednesday | 89.38 |
| 6 | Friday | 169.33 |
| 7 | Saturday | 1.76 |
+---------+-----------+---------------+
6 rows in set (0.00 sec)
The DDL and queries in this post have been tested. Let me know if you need the data :)