on dbcombobox1 change update dbcombobox2
lazarus / 16-Databases

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Danyfirex · 2015-07-01 17:47

hi mate. it's me again. is there a way (I mean using dbcombobox
properties to do that). I mean this.

I have my database.db

has many tables some table field is a reference to another table
field.

example tables:

Table1->Person
ID|Name|idCountry|idCity|idTown

table2->Country
ID|country_name

table3->City
ID|city_name

table3->town
ID|town_name

is there some properties that let me fill the combo with all the field
that is refered to.


Combocountry1=if i choose some contry combocity get all cities that
are refere to that country.

combocity2 if i choose a city my combotown3 get all town that are
refere to that city.

combotown3 here make some similar but with  another things.


I know this can be done using my dataset but I asking if exist a fast
way with the dbcombobox properties to do that more
flexible,fast,practical.


Saludos

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taazz · 2015-07-01 17:51

Use DBLookupComboBox instead.

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Danyfirex · 2015-07-01 18:26

mate can you provide me scheme how to se the propierties. I'm trying
with DBLookupComboBox but I can't figure me how to do it.

Saludos

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taazz · 2015-07-01 18:42

use a query that returns all the records from the country table and a
second query that returns all records of the person table and link
them to datasources lets name them QryPerson for the person query
DSPerson for the person datasource and QryCountry, DSCountry for the
country controls respectively. DBLookupCombobox has 2 groups main
groups of properties 1) the data to be changed when the combobox is
used to select a value and 2) the query that provides the values you
can choose from.
in the first group are the properties Datasource, Datafield which must
be linked to the DSPerson and IDCountry field and in the second group
are the properties Listsource linked to dsCountry, listField must be
linked to the Country_name field and KeyField that must be linked to
the DSCountry.ID field.
After that if you use the default property values every time you
select a country in the dblookupcombobox it will change the active
record's idcountry field value the new one selected. All filling and
setting is taken care for you internally.

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Danyfirex · 2015-07-01 20:30

Thank you very much mate that's help me so much. so I have another
problem. The code work well. but For example:

when I select my contry in my dblookupcomboboxContry my
dblookupcomboboxCity get update so. I want to show just the cities
from that contry but it show me all my cities. show I work with query
on the change event. o could be done with the properties.

Saludos

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taazz · 2015-07-01 20:40

It can be done with properties yes. You make sure the city query
includes a parameterize where statement. Something along the lines of
Code: [Select]QryCity.SelectSql.text := 'Select * from City where
IdCountry = :ID' I'm writing id as the name of the id field in the
country query, it must much what ever the country query uses for the
ID field name exactly, then you set the qryCity.DataSource property to
the dsCountry. for more details visit
http://wiki.freepascal.org/MasterDetail

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Danyfirex · 2015-07-01 20:43

I solved that part by this way.

on the event change make a new query on the City refered to my contry
idContry value.

Code: [Select]QryCity.Close;
QryCity.SQL.Text:='SELECT * FROM City where
idCoutry='''+inttostr(LookDBCountry.KeyValue)+'''';
QryCity.Open;   
So if there is another way let me know it.

¿taazz by properties would be? Sorry if I ask too much. so there is
not good reference using that control.

Thank you very much Mr. taazz.

I'll look the link. Thank you. I'll come back with the result.

Saludos