Check duplicates in TADOQuery

[karl Jonson 0]

I have this procedure:

procedure FindDuplicate(Qry : TADOQuery);

The Qry contains just 1 column: "Codes"
Which the most efficient way to check that "Codes" column doesn't contain any duplicates ?

TIA

[Lajos Juhász 293]

What is the metric for efficiency? You would have to iterate the query and for every record check the value in a memory structure if it's there you have duplicate if not insert into it.

 

You can store the list in an array, list or a hash table.

[PeterBelow 238]

22 hours ago, karl Jonson said:

I have this procedure:

procedure FindDuplicate(Qry : TADOQuery);

The Qry contains just 1 column: "Codes"
Which the most efficient way to check that "Codes" column doesn't contain any duplicates ?

TIA

Modify the SELECT statement for the query to include an ORDER BY clause for the code column. Then you can walk over the query result and just compare the current record's code to the one from the previous record (which you remember in a local variable in the loop).

You can also formulate a SELECT statement that just returns the duplicates of course...

[skyzoframe[hun] 4]

select codes, count(*) as duplicate
from data1
group by codes
having count(*)<>1
order by duplicate desc

https://dbfiddle.uk/nYtX1oTz