insert …select … count … on duplicate key update error

问题

I created a table to hold counts of work orders by asset tag. I have 2 fields, asset_tag (which is unique) and the wo_count. I am trying to write a query that will insert/update the counts in the table. Through research on ON DUPLICATE KEY UPDATE, I have come up with this, but am getting unknown column errors.

INSERT INTO mod_workorder_counts (asset_tag, wo_count) 
    (SELECT t.asset_tag, count(*) AS cnt 
        FROM mod_workorder_data t
        WHERE t.asset_tag IS NOT NULL 
     GROUP BY t.asset_tag)
ON DUPLICATE KEY UPDATE mod_workorder_counts.wo_count = t.cnt

When I run this I get #1054 - Unknown column 't.cnt' in 'field list'. I am not sure how to use the count values in the update.

回答1:

Once you reference it as "cnt", you no longer need the "t." portion. You should reference it as just "cnt".

来源：https://stackoverflow.com/questions/5687971/insert-select-count-on-duplicate-key-update-error