Ascending and decreasing ordination in the Clientdataset

Question

I have to order the clientdataset 3 fields at the same time:

1 - Assets(0 or 1)
2 - date(dd/mm/yyyy)
3 - name

The problem is that I need to make different ordinations for each of them, the first decreasing and the other increasing.

There’s a way to do that in clientdataset or some other approach will be required?

Answer 1

Yes, it is possible. Just use the indexes offered by Dataset.

I find it interesting to talk a little about the indices:

There are basically two types of indices in Delphi: The temporary and the persistent.

Indices temporary are created using Indexfieldnames. Let’s assume you have a Clientdataset with Fields: Primeironome, Ultimonome and Datanascimento. If I wanted to sort my records by last name and then by first, I could do that:

ClientDataSet1.IndexFieldNames := 'UltimoNome;PrimeiroNome';  

At any time this can be changed.

ClientDataSet1.IndexFieldNames := 'UltimoNome';  
// etc...

When you do this Delphi creates the indices internally and associates them to the dataset. That’s why they’re called temporary.

In your case this will not suit you, I wrote only for enrichment. In your case an index persistent will be more appropriate:

Indexes persistent are created in the Indexdefs of your Dataset. So you can, for each index, define a number of properties. They are used in the same way as indexes temporary, just use the name given to the index persistent when they are created in design-time.

To create an Index Persistent in Runtime, just use the code snippet below:

with ClientDataSet1.IndexDefs.AddIndexDef do 
begin 
  Name := 'OrdenarUltimoPrimeiroNomedx'; 
  Fields := 'UltimoNome;PrimeiroNome';
  Options := [ixDescending, ixCaseInsensitive]; 
end; 
ClientDataSet1.IndexName := 'OrdenarUltimoPrimeiroNomedx'; 

EDIT: I talked so much and ended up not giving an exact answer.

You can create as many persistent indexes as you need:

with ClientDataSet1.IndexDefs.AddIndexDef do 
begin 
  Name := 'OrdenarUltimoPrimeiroNomedx'; 
  Fields := 'UltimoNome;PrimeiroNome';
  Options := [ixDescending, ixCaseInsensitive]; 
end; 

with ClientDataSet1.IndexDefs.AddIndexDef do 
begin 
  Name := 'DataNascimentoAscdx'; 
  Fields := 'DataNascimento';
  Options := [ixAscending]; 
end; 

ClientDataSet1.IndexName := 'DataNascimentoAscdx;OrdenarUltimoPrimeiroNomedx'; 

In the above example I will sort by birth date Ascendant and then by Last Name and First Descending Name.

If you want a good reference, I suggest you access this link:

Answer 2

Depending on the version of Delphi you have can do so:

ClientDataSet1.IndexFieldNames := 'UltimoNome:D;PrimeiroNome'; 

the statement ':D' indicates that it is in descending order, if leaving without anything the cds understands that it is Ascendant. If your Delphi does not work, then use the persistent index.