SQL Query relating to grouping entries - sql

Question

When I normalised my database, I used a text value to group together entries giving them the same foreign key. However, I also had 2 other fields prior to normalisation which used reference numbers to group together entries, one into pairs of entries and one into groups of entries. Because these grouped entries did not necessarily have the same text value, some entries will have been left out of the grouping (shared foreign key id).
I need a query which selects all entries which share a PairRef or GroupRef where the entries in that group do not all have the same ForeignKeyID.
Example:
ID PairRef GroupRef ForeignKeyID TextValue (in linked table2)
1 25 25 123 'Text value 123'
2 25 25 255 'Text value 255'
3 1 50 201 'Text value 201'
4 1 50 201 'Text value 201'
5 2 50 202 'Text value 202'
6 2 50 202 'Text value 202'
7 3 50 203 'Text value 203'
8 3 50 203 'Text value 203'
I then need to be able to edit the data to group them together. The problem is that in order to do this, I would need the query to be from more than one table because I need to see the text associated with the foreign key. I have found that using phpMyAdmin, although I can create queries from more than one table using inner joins, the results of these queries cannot be edited in the way that queries from one table can.
I guess the alternative would be to do an update query on the query results. Could you give an example of a quick and easy way of doing an update query on query results, without losing the original query which needs to be used repeatedly.
In the above example, for the regrouping of ID 1 and ID 2 which share the same PairRef, I would need to physically look at TextValue 123 and 255 and depending which one was the more appropriate text label, I would decide on which entry to change. Let's say that 'Text value 123' was the value I wanted to retain for that grouping. I would update ID 2 to ForeignKeyID 123, which would obviously automatically change the TextValue for that entry to 'Text value 123'.
For the regrouping of IDs 3 to 8, which share the same GroupRef, if I decided after looking at the data to re-group them all as 'Text value 201', I would change IDs 5,6,7 and 8 to ForeignKeyID = 201, which would automatically change all the TextValues for those entries to 'Text Value 201'.
IDs 1 to 8 would then no longer appear on the query results because the grouping problem would have been resolved and they would no longer meet the query criteria.
I need to find the easiest way possible of doing this, as grouping entries together is one of the main purposes of the databases and there is a lot of this editing to do.
Thank you

Answer 1

For the first part (select all entries which share a PairRef or GroupRef where the entries in that group do not all have the same ForeignKeyID), the following query can be used. It groups by PairRef and selects PairRefs which have more than 1 distinct ForeignKeyID. Then, all entries which have these PairRefs are selected. Similarly, the data is grouped by GroupRef also. All GroupRefs which have more than 1 distinct ForeignKeyID are selected. Then, all entries which have these GroupRefs are selected.
SELECT
T1.*
FROM Table1 T1
INNER JOIN Table2 T2
ON T1.ForeignKeyID = T2.ForeignKeyID
WHERE PairRef IN
(
SELECT
PairRef
FROM table1
GROUP BY PairRef
HAVING Count(DISTINCT ForeignKeyID) > 1
)
OR GroupRef IN
(
SELECT
GroupRef
FROM table1
GROUP BY GroupRef
HAVING Count(DISTINCT ForeignKeyID) > 1
);
For the second part (edit the data to group them together), I do not understand why you would need to see the TextValue from table2 (if it is corresponding to ForeignKeyID in table1). Anyway, once you have seen the PairRefs / GroupRefs, which have different ForeignKeyID values, you can run an update statement for each PairRef / GroupRef, since it seems like a manual process.
UPDATE Table1
SET ForeignKeyID = <ForeignKeyID to be set>
WHERE PairRef = <PairRef to update>;
UPDATE Table1
SET ForeignKeyID = <ForeignKeyID to be set>
WHERE GroupRef = <PairRef to update>;
You may need to run the first query again to check the data, because the UPDATE query for GroupRef might result in different values for PairRef.
Here is a SQL Fiddle demo. Thank you, #JohnLBevan for the stub.