You can use GROUP_CONCAT
:
SELECT person_id,
GROUP_CONCAT(hobbies SEPARATOR ', ')
FROM peoples_hobbies
GROUP BY person_id;
As Ludwig stated in his comment, you can add the DISTINCT
operator to avoid duplicates:
SELECT person_id,
GROUP_CONCAT(DISTINCT hobbies SEPARATOR ', ')
FROM peoples_hobbies
GROUP BY person_id;
As Jan stated in their comment, you can also sort the values before imploding it using ORDER BY
:
SELECT person_id,
GROUP_CONCAT(hobbies ORDER BY hobbies ASC SEPARATOR ', ')
FROM peoples_hobbies
GROUP BY person_id;
As Dag stated in his comment, there is a 1024 byte limit on the result. To solve this, run this query before your query:
SET group_concat_max_len = 2048;
Of course, you can change 2048
according to your needs. To calculate and assign the value:
SET group_concat_max_len = CAST(
(SELECT SUM(LENGTH(hobbies)) + COUNT(*) * LENGTH(', ')
FROM peoples_hobbies
GROUP BY person_id) AS UNSIGNED);
Timestamps in MySQL are generally used to track changes to records, and are often updated every time the record is changed. If you want to store a specific value you should use a datetime field.
If you meant that you want to decide between using a UNIX timestamp or a native MySQL datetime field, go with the native format. You can do calculations within MySQL that way
("SELECT DATE_ADD(my_datetime, INTERVAL 1 DAY)")
and it is simple to change the format of the value to a UNIX timestamp ("SELECT UNIX_TIMESTAMP(my_datetime)")
when you query the record if you want to operate on it with PHP.
Best Answer
PowerDesigner tries to keep track of the links between CDM and PDM objects. If you change (denormalize, or rename) something in the PDM, change something in CDM, and generate again, it will use this linking information to update your PDM properly, rather than just generating a default PDM from the CDM.
Which version of PowerDesigner are you using? You should be able to create a PDM targetting a MySQL DBMS; outside PowerDesigner create an ODBC data source after installing Connector/ODBC; connect to your data source with
Database > Connect
; and generate your model inside your database withDatabase > Generate Database
.Don't know...