Question

I need to created a query in MS Access 2010 that combines data from 4 different tables in one column.

The tables are defined as below;

Table 1: date, country, channel, calls_in
Table 2: date, country, channel, calls_out
Table 3: date, country, channel, email
Table 4: date, country, channel, chat

The query should look like:

Query 1: Date, country, channel, contacts 

The contacts column should combine the 4 contact types (i.e. calls_in/out, email and chat) for the appropriate date, country and channel.

All 4 tables have the same dates and countries. Channel is specific to each table.

I have been trying to get this done but can’t get my head around it.

Answer 1

You might be after this:

SELECT
  all_contacts.date,
  all_contacts.country,
  all_contacts.channel,
  "calls in: " & [calls_in] & ", calls out: " & [calls_out] & ", email: " & [email] & ", chat " & [chat] AS contacts
FROM
  ((((select date, country, channel from [Table 1] union
      select date, country, channel from [Table 2] union
      select date, country, channel from [Table 3] union
      select date, country, channel from [Table 4])  AS all_contacts
  LEFT JOIN [Table 1] ON (all_contacts.channel = [Table 1].channel) AND (all_contacts.country = [Table 1].country) AND (all_contacts.date = [Table 1].date))
  LEFT JOIN [Table 2] ON (all_contacts.channel = [Table 2].channel) AND (all_contacts.country = [Table 2].country) AND (all_contacts.date = [Table 2].date))
  LEFT JOIN [Table 3] ON (all_contacts.channel = [Table 3].channel) AND (all_contacts.country = [Table 3].country) AND (all_contacts.date = [Table 3].date))
  LEFT JOIN [Table 4] ON (all_contacts.channel = [Table 4].channel) AND (all_contacts.country = [Table 4].country) AND (all_contacts.date = [Table 4].date);

Since MS-Access doesn’t support FULL OUTER JOINS, and doesn’t have an aggregate function like GROUP_CONCAT, I’m left joining a UNION subquery that contains all of the dates, countries and channels with every table, and I’m then combining all the contacts (calls_in, calls_out, email and chat) into one cell.