(solved) basic question-Tzquery
lazarus / 16-Databases

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aliboy · 2012-11-24 13:11

hi dear

i read this tutorial and  have a basic question about writing query.

http://wiki.freepascal.org/Zeos_tutorial


QuoteDrop a ZConnection.
Set your User, Password, Host, Port and Protocol (and any other params
if needed).
Set Connected to True.
Drop a ZQuery (do not mistake with ZReadOnlyQuery).
Set the Connection to your active ZConnection.
Set the Sql property to something like SELECT * FROM MyTable
Set Active to True.
Drop a DataSource from the [Data Access] tab.
Set the DataSet to your active ZQuery.
Drop a DBGrid from the [Data Controls] tab.
Set the Datasource to your DataSource.
If all is ok you should now be able to see the records from your table
 (notice: I used  ZConnection1,ZQuery1,Datasource1,DBGrid1  and can
make connection to database )

and i added this code to FormCreate  (onCreate event) to show data in
DBgrid.

Code: [Select]ZQuery1.SQL.Clear;
  ZQuery1.SQL.Add('select * from tlb');
  ZQuery1.ExecSQL;
my problem occurs when goning to ENABLE ZQuery but facing with this
error:
Quote SQL Query is empty
I would like to get data from database with write query (not change 
SQL property of ZQuery1).
is there need other object such as ZUpdateSQL1?


thanks a lot.

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vfclists · 2012-11-24 14:37

Shouldn't it be ZQuery1.Open rather than ZQuery1.ExecSQL?

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aliboy · 2012-11-24 15:38

Quote from: vfclists on November 24, 2012, 03:37:34 pmShouldn't it be
ZQuery1.Open rather than ZQuery1.ExecSQL?

when i used ZQuery1.ExecSQL project loaded with no error and Dbgrid
had no data,

Code: [Select]ZQuery1.SQL.Clear;
  ZQuery1.SQL.Add('select * from tlb');
  ZQuery1.ExecSQL
 and when used ZQuery1.Open  had a memory error.

Code: [Select]ZQuery1.SQL.Clear;
  ZQuery1.SQL.Add('select * from tlb');
  ZQuery1.open
i think connecting to database has a tip that i search for it.
actually i have 2 problems 1-SQL Query is empty   2-i would like to
write query to get data on   FormCreate

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EgonHugeist · 2012-11-24 17:42

You are posting everywhere around and nobody knows if your threads are
solved or not. 

TZQuery.Open; opens a resultset and fetches the data from the
database.

TZQuery.ExecSQL; simply executes a statement but no resultset is
retrived. Only an updatecount is validated.

What is a memory-error? Give all peoples more details to help you
getting in. Also read the tutorials.

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aliboy · 2012-11-24 22:10

Ok.thanks.

I install Lazarus 1.0.2 .

I create a form (form1) and drag these objects to it and for each

component change  some properties:
1-Zconnection1

clientcodepage=utf8
conncted:ture
database:amahi
libararylocation:G:\programming\Lazrus_P\DataBase\Example2\libmysql.dl
l
port:3306
user:root
password:
protocol:mysql-5

(amahi is my database name at mysql) (my username has no password so
it is blank)

2-ZQuery1

connection:ZConnection1

(in default   Active:false i didn't change it )

3-datasource1

dataset:ZQuery1

4-dbgrid1

Datasource:Datasource1

5-form1
onCreate:

 ZQuery1.SQL.Clear;
  ZQuery1.SQL.Add('select * from tlb');
  ZQuery1.ExecSQL;

with this changes, the project ran but dbgrid couldn't show data.
so for ZQuery1  change Active to true and Lazarus says:
Sql query is empty.
for avoiding this error must add a sql command to SQL property of
ZQuery1.(for example: select * from tlb) ==>and dbgrid shows data

I would like to get data from database with write query (not change 
SQL property of ZQuery1).
OK?

thank you.

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aliboy · 2012-11-28 21:32

it solved:

onCreate form must add this code:

  Code: [Select]ZQuery1.SQL.Clear;
  ZQuery1.SQL.Add('select * from s');
  ZQuery1.Open;
  ZQuery1.Active:=true;

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BigChimp · 2012-11-29 10:33

Glad you got it solved and thanks for posting.

If you think you can update the tutorial so others can benefit, please
be my guest. Don't worry too much about the English or formatting as
others can always fix that - it is much more difficult to write
content than to correct some spelling errors.

A tiny hint: rather than using the Insert Quote button around your
code on your posts, try the Insert Code button next to it (that looks
like #)