Question

I need to update cells within a specific column based upon ids in another column. The column names are Prod_ID, Lang_ID and Descr:

Prod_ID | Lang_ID | Descr
--------+---------+------
A101    | 1       | TextA
A101    | 2       | TextB
A101    | 3       | TextC

For a group of rows with the same Prod_ID, I need to replace all subsequent descriptions (Descr column) with the description of the first row. The row with the correct description has always Lang_ID = 1. Also, the table may not be sorted by Lang_ID.

Example: TextA (Lang_ID = 1) should replace TextB and TextC because the Prod_IDs of the rows match.

Answer 1

Assuming that the correct description is always in the row of a group of rows with the same Prod_ID where Lang_ID has the smallest value, this MySQL query should work:

UPDATE your_table AS t1
    JOIN (
        SELECT Prod_ID, Descr
        FROM (
            SELECT *
            FROM your_table
            ORDER BY Lang_ID
        ) AS t3
        GROUP BY Prod_ID
    ) AS t2
    ON t1.Prod_ID = t2.Prod_ID
SET t1.Descr = t2.Descr;

The above can be used e.g. if Lang_ID is a primary or unique key. It also works if the corresponding Lang_ID has always the same minimum value (e.g. = 1) but in that case much less complex queries like this one are possible.