Programming with dBASE - calculated field type

Author

calculated field type

Moses Hanna

2005-12-28, 8:23 pm

Hi
I want to add a calculated field.
The new field is the total of 4 numeric fields in the same table
I coded the following in the query's on open event
the query name is jdetails1

function jdetails1_onOpen
f = new Field()
f.fieldName := "Totals"
f.beforeGetValue := {|| this.parent["val1"].value
+this.parent["val2"].value + this.parent["val3"].value +
this.parent["val4"].value }
this.rowset.fields.add( f )
return

The Field type is coming character and the result is not numeric
any help to get the calc field value as a numeric total of 4 fields?
Thanks
Moses

*Lysander*

2005-12-29, 7:23 am

In article <otHN94BDGHA.1800@news-server>, mosesjhanna@hotmail.com=20
says...

> The Field type is coming character and the result is not numeric
> any help to get the calc field value as a numeric total of 4 fields?

There's a more easy way, though maybe Q&D, but works perfectly for me in=20
all scenarios:

Put the calculated field already into your sql-statement!

jdetails1.sql =3D ;
"SELECT "+;
" val1, "+;
" val2, "+;
" val3, "+;
" val4, "+;
" val1 + val2 + val3 + val4 AS f_totals "+;
"FROM "+;
" The_Table "

This will create a new calculated field named "f_totals" which is read-
only and "virtual", which means that it is only generated at runtime and=20
will not really be saved into the table.

--=20
ciao,
Andr=E9

Michael Nuwer [dBVIPS]

2005-12-29, 9:23 am

I have seen this problem before, but I can not reproduce it at this
time. So I'm working from memory. Try adding a length property to the code:

f = new Field()
f.fieldName := "Totals"
f.length := 8 // <<<<<<
f.beforeGetValue := ...

Moses Hanna wrote:
> Hi
> I want to add a calculated field.
> The new field is the total of 4 numeric fields in the same table
> I coded the following in the query's on open event
> the query name is jdetails1
>
> function jdetails1_onOpen
> f = new Field()
> f.fieldName := "Totals"
> f.beforeGetValue := {|| this.parent["val1"].value
> +this.parent["val2"].value + this.parent["val3"].value +
> this.parent["val4"].value }
> this.rowset.fields.add( f )
> return
>
> The Field type is coming character and the result is not numeric
> any help to get the calc field value as a numeric total of 4 fields?
> Thanks
> Moses
>
>

Ronnie MacGregor

2005-12-30, 11:23 am

In article <otHN94BDGHA.1800@news-server>, mosesjhanna@hotmail.com
says...

> I want to add a calculated field.
> The new field is the total of 4 numeric fields in the same table
> I coded the following in the query's on open event
> the query name is jdetails1
>
> function jdetails1_onOpen
> f = new Field()
> f.fieldName := "Totals"
> f.beforeGetValue := {|| this.parent["val1"].value
> +this.parent["val2"].value + this.parent["val3"].value +
> this.parent["val4"].value }
> this.rowset.fields.add( f )
> return
>
> The Field type is coming character and the result is not numeric
> any help to get the calc field value as a numeric total of 4 fields?

You could be falling foul of dBASE automatic type conversion here.

Untested, but my understanding is that when you create a calculated
field, dBASE has no way of knowing what data type is required, defaults
to char - "empty string", and the beforeGetValue will then convert a
numeric value to the already defined string or char data type.

Try :

f.value = 0 // numeric zero

or

f.value = null

in your definition code to force, or allow, the correct data type, and
see if this solves your problem.

--
Ronnie MacGregor
Scotland

www.dBASEdeveloper.co.uk

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