I am trying to use Macros in FireDAC to Preprocess my SQL Queries. I have a TADQuery object on a Data Module with the SQL set to something like:
Select * from MyTable
join OtherTable on MyTable.Key = OtherTable.Key
&Where
Then in my code I do this:
WhereClause = 'stuff based on my form';
Query.MacroByName('Where').AsRaw := WhereClause;
Query.Open;
This has worked great for complicated queries because it lets me make sure my fields and join conditions are correct using the SQL Property editor.
My problem is when the SQL statements ends up invalid because of my where clause. Is there any way to see the SQL after pre-processing that is going to be executed? Right now I am catching the FireDac errors and showing the SQL that is on EADDBEngineException object. However that is still showing my original SQL with the macros. If I can't get to it after the error happens is there anyway to force the Macro replacement to take place so I can look at the SQL in the debugger to help me see what is wrong.
If it matters I am connecting to a MS Access database with the goal of moving to SQL Server in the near future.
Apart from using Text property, to monitor what SQL is actually going to the database engine, consider using the "FDMonitor" FireDAC utility. According to the DokWiki pages (below):
drop a TFDMoniRemoteClientLink component on your form,
Set its Tracing property to True,
Add the MonitorBy=Xxx connection definition parameter to your existing FDConnection component. You can do this in the IDE object inspector, by selecting your FDConnection component, expanding the Params property, and setting MonitorBy to mbRemote.
Note that the TFDMoniXxxxClientLink should come before TFDConnection in the data module or form creation order, so adjust this by right clicking on the form or data module, then Creation Order, and moving the TFDMoni.. component above the FDConnection.
Also, it's helpful in the options of the TFDMoniXxxxClientLink, to disable most of the events being recorded, otherwise all the data returned is also shown in the FireDAC monitor. Expand the EventKinds property, and turn all the event kinds off, except for perhaps ekConnConnect, ekConnPrepare, and ekCmdExecute.
Then open the FireDAC Monitor from the IDE, (Tools > FireDAC Monitor). Start your app only once the monitor is running. Double click on a trace event (in the Trace Output tab), and you will see the actual SQL sent to the database in the bottom pane.
It also seems likely that adding the EventType of ekConnPrepare as mentioned above, would show you when the query's Prepare is called, but I haven't played enough with it say for sure.
Please see the following pages on the DocWiki for more information:
Overview: FDMonitor
How to: Tracing and Monitoring (FireDAC)
Other FireDAC utilities: Utilities (FireDAC)
(Just to remove this question from list of unanswered questions)
From comments:
Well, I've roughly checked what's happening there and I'm still not
sure if calling Prepare (which is useless for you as I get) is the
minimal requirement to trigger that preprocessing. Though, the
preprocessed SQL, the one which is sent to the DBMS you can access
through the Text property (quite uncommon name for such property). – TLama Feb
21 '14 at 8:18
Related
I am sure that I'm overlooking some simple thing here.
With a FireDac connection, if I use a SQL query with a WHERE clause that, due to the content of the search parameter, would normally return an empty result set, the OPEN command returns an error instead "Cannot open / define command, which does not return result sets". Is this by design ? Every other Delphi DB connection tool I have used simply returns an empty result set with a record count of 0.
******************************* April 16
I believe Victoria is on the right track. I had never used Firedac before so assumed it was the behaviour as designed. However if I communicate with the same RDBMS using the MS SQL driver, I do not see this happen, so I suspect it is on the Datasnap end.
My name is Stefano Fanti,I am a developer in Plexa.We are actually using your component ( FireDAC ) and I am contacting you in order to solve some
problems we have not been able to fix ourself.
In our company we decided to port a legacy 3-Tier DATASNAP application written on Delphi7 for the new environment Delphi XE7 , and we decided to use the new components library FireDAC too.
Our application is built in this way: a Client side using TClientDataSet directly connected to the Server side with TDataSetProvider/MIDAS and TTable TQuery TDatabase components (BDE)
We replaced BDE components with the related FireDAC ( FDConnection , FDTable and FDQuery ) without issues and we started testing thinking anyway it was not needed to perform it.
After some test , a couple of issues have arosen : the first problem is related to the modifications performed on DB ( MS SQL Server ) , the second is related the the reopening of the table after applying the modifications.
In our case , the RequestLive=True property ( default ) , does’nt allow to apply modifications ( Post/ApplyUpdates) to the Database.
Assigning RequestLive = False , we are able to apply modifications on all table’s records except the first, the last giving us the error .
The above anomaly have been verified on each Database table . However all database tables have the primary key defined properly.
Trying to use FireDAC Help I read the option RequestLive=False excludes fiMeta from Fetch,Options, preventing the component to use the primary key of the table, being otherwise seen correctly in any other case.
After several trials I found two configurations applied to the Server side, allowing us to achieve the result.
First configuration
FDTable.RequestLive= False
FDTable.UpdateMode = upWhereKeyOnly
with FProvider.DataSet.FieldByName (pkField) do
ProviderFlags: = ProviderFlags + [pfInKey];
Second configuration
FDTable.RequestLive= False
FDTable.UpdateMode = upWhereAll
TDataSetProvider.UpdateMode=upWhereAll
The above configurations give us the possibility to apply modifications to tables without errors , but nevertheless don’t allow us to solve the second problem : reopening of the tables for each operation. Indeed , the BeforeOpen and AfterOpen managers are executed each time.
What can I do to avoid the Table to be needless reopened after each modification ?
Are the configurations used to apply modifications correct , or maybe another solution exist allowing us to avoid code modifications causing us to lengthen development times ?
Thank you in advance for your help.
Best regards
Stefano Fanti
I was using UniDac for a long time now and decided to move on to FireDac as it has good Asynch methods after moving on i saw that none of my data editing works anymore it gives me an error:
[FireDAC][Phys]-330. Cannot generate update query. Update table undefined.
What I am trying to do here is i have a TFDStoredProc component who gets all the data from the database and lets me edit it, with unidac I could easily edit the data without any problem like this:
StoredProc.Edit;
StoredProcCreatedID.Value := SomeValue;
StoredProc.Post;
and it worked, but with AnyDac it doesn't, I tried specifying manually the UpdateTable which leads to another problem:
[FireDAC][Phys][ODBC][Microsoft][SQL Server Native Client 11.0][SQL Server]Invalid column name 'CreatedID'.
I am using Microsoft SQL Server 2012 FireDac 8.0 and stored procedures for getting back results any ideas?
P.S.
The query looks like this
SELECT
CreatedBy as CreatedID,
usr.UserName as CreatedBy
FROM
Sales
LEFT JOIN
Users usr ON usr.ID = Sales.CreatedBy
it looks like the FireDac update builder doesn't recognize the aliases on the fields, any help would be appreciated.
Well i figured out what was the issue, it seems that if you specify a alias in the query for a field the Origin property will be set to the alias and not the real field i downloaded CNPack a must have for a delphi developer also its free, ran the component selector and changed all my aliased fields to their real fields and it works, but this is still a big issue in FireDac component because it doesnt recognize the aliased fields, lets hope it will be fixed in the future as to specify for every query what table it should update and what fields that just allot of work if you are migrating from a big project in my case 220+ stored procedures.
I have a very large block of SQL that I am trying to execute inside of Delphi, against a Microsoft SQL Database. I am getting this:
Multiple-step OLE DB operation generated errors.
Check each OLE DB status value, if available. No work was done.
The script has multiple sql IF statements followed by BEGIN and END blocks with invocations of stored procedures, declaration of variables, and EXEC inside that. Finally it returns some of the variable values by SELECT #Variable1 AsName1,#Variable2 AsName2....
The above multi-step error is coming in as an OLEException from ADO, not from the Delphi code, and happens after all the SQL exec-stored-procedure have occurred, and therefore I suspect it's firing this OLE exception when it reaches the final stage which SELECT #Variable1 AsName1,... to get back a few variable values for my program to see them.
I know about this retired/deprecated MS KB article, and this is unfortunately not my actual issue:
http://support.microsoft.com/kb/269495
In short that KB article says to fix a registry key and remove "Persist Security Info" from the connection string. That's not my problem. I'm asking this question because I found the answer already and I think that someone else who gets stuck here might not want to waste several hours finding potential issues when there are several that I have found after searching for solutions for several hours. Anyone who wants to add another answer with different options, is fine, and I'll select yours if it's reproducible, and if necessary I'll turn this one into a Community Wiki because there could be a dozen obscure causes for this "ADO recordset is in a bad mood and is unhappy with your T-SQL" exception.
I have found several potential causes that are listed in various sources of documentation. The original KB article in the question suggests removing the 'Persist Security Info' from my ADO connection string, however in a standalone test in an application with just a TADOConnection and a single TADOQuery, the presence or absence of Persist Security Info had no effect, nor did explicitly setting it True or False.
What DID fix it was removing this CursorType declaration:
CursorType=ctKeyset
What I have learned is that bidirectional ADO datasets are fine for SELECT * FROM TABLE in ADO but are not so fine for complex SQL scripts.
Potential source of this error is updating char field with large value.
Example: Form has edit box with max length property set to 20 characters and Oracle database table has field defined as char(10).
Updating with 10 characters (or less) will work fine while updating with more then 10 characters will cause 'Multiple step...' error on ADOQuerry.UpdateBatch().
You also have to know that CHAR will allways have 20 characters. Consider Trimming value in edit box. CHAR behaves different than VARCHAR2 type.
If you have a query with parameter ,check the number of parameters in the query is matched with script...!
I need a delphi component for Delphi 2007 win32 that have features like Google search text box.
** While User writing search key it should fill/refresh the list with values, and user can select one of them.
**User can go up and down list and can select one of them.
**List should contain codes and text pair, so user can select text and I can get code for database operations.
(Google can highlight the search text in List but I think it is not possible with Delphi 2007, so it is not expected.)
I tried Dev Express TcxMRUEdit, however it doesn't meet my needs
Since you have DevExpress, why don't you try the cxLookupComboBox in lsEditMode and with ImmediateDropDown = True?
Check out woll2woll components. The TLookupcombobox has done this since Delphi 3 (or earlier). This is not spam, I just use the library.
http://www.woll2woll.com/
I also had the same problem and unfortunately didn't find a suitable component. I was also inspired from google.
So it turned out to be easier for me to "simulate a component" by using an editbox and a grid placed under it. As the user types something in the editbox the query refreshes and the proper resulst are shown in the grid. I have many columns in the grid, the query results try to match all the fields (so if I type 'po', the query will return all records where any field is like 'po%'). I also added a delay of 500ms after the user types to avoid to run too many unnecessary queries (another aproach could be to kill the thread as the user strikes a new key, if the query is run in a thread).
In this way I obtained the required functionality, even if without higlighting the search text, anyway my users are delighted by this.
In every place I am using this "component" I am attaching a query at runtime so it can be used in many different forms.
I somehow was also inspired by the skype UI: when you display the lsit of contacts you can type something and the contacts will be filtered accordingly (skype uses an editbox + grid/listbox).