Question

I have a mysql table that have several records linked to one particular tag. For example, this query

SELECT * FROM table1 WHERE tag = 'tag1'

will return this

equipment_id   |   tag   |   acquisition_cost   |   purchase_date   | user
1                  tag1         200.05                 null            null
5                  tag1          null                02-02-2012        null
19                 tag1          null                  null            jsmith

I would like to combine all the results that have the same tag, and insert into a new table so that I get this:

SELECT * FROM table2 WHERE tag = 'tag1'

equipment_id   |   tag   |   acquisition_cost   |   purchase_date   |    user
[]                  tag1         200.05                 02-02-2012       jsmith

Any suggestions?

Answer 1

If there is only one value per column per tag then you can use a query like this:

SELECT 
  tag,
  MAX(acquisition_cost),
  MAX(purchase_date),
  MAX(user) 
FROM `table1`
GROUP BY tag

If there is more than one value then I’d highly not recommend collapsing the data like this – you should rethink your design.