• When queries are implemented via SQL strings, each new string must be prepared.
• With parameterized queries, the query is prepared only once. Then the application changes the parameters and runs the same query again without Delphi having to prepare it again.
• In addition, parameters are sent as binary (as opposed to string) data. this means that dates and blobs can be sent as parameters.

References

• Why You Can't Pass a List to an InterBase SQL Param by Craig Stuntz has a short section called About Parameterized Queries

IBQuery	Allows both Select (via Open) and non-Select SQL (via ExecSQL) statements
IBUpdateSQL	Allows only non-Select SQL statements - Should be linked to a TIBQuery component via the TIBQuery.UpdateObject property
IBDataSet	Allows both Select and non-Select SQL statements - to prepare a query, a select statement is required and all the non-null non-Select SQL statements are also prepared. Each SQL type is implemented via an automatically provided IBSQL component. These must be individually accessed to run their queries. This component provides a way to add several paramertized queries to an application using a single component.
IBSQL	Unidirectional with no interface to data-aware controls - each IBDataSet includes 4 of these.

• select statements are inherintly read only
• Table components provide read and write abilities ... but they are really slow
• The non-Select SQL statements (insert, update, delete) provide a way to modify the data

procedure TBasicDataModule.ExecuteSQL(s: string);
begin
  IBQuery_Basic.SQL.Text := s;
  IBQuery_Basic.ExecSQL;
  IBQuery_Basic.SQL.Text := 'commit'; // lets other users see the changes
  IBQuery_Basic.ExecSQL;
end;   // ExecuteSQL

procedure TBasicDataModule.ExecuteSelectSQL(s: string);
begin
  IBQuery_Basic.Close;
  IBQuery_Basic.SQL.Text := s;
  IBQuery_Basic.Open;
end;   // ExecuteSelectSQL

For test purposes, I have a form with 2 Memo fields and 2 buttons. In general

• active must be false to modify the SQL text
• active must be true to execute ExecQuery
• Individual non-select queries are run by accessing their internal components (This was not documented)

  IBDataSet1.QModify.ExecQuery;

• The test queries do NOT contain semicolons (they are optional)

procedure TForm1.Select_UIButtonClick(Sender: TObject);
begin
  IBDataSet1.Active := false;
  IBDataSet1.SelectSQL.Text := Select_UIMemo.Text;
  IBDataSet1.Prepare;
  IBDataSet1.Active := true;
end;

procedure TForm1.Modify_UIButtonClick(Sender: TObject);
begin
  IBDataSet1.Active := false;
  IBDataSet1.ModifySQL.Text := Modify_UIMemo.Text;
  IBDataSet1.Prepare;
  IBDataSet1.Active := true;
  IBDataSet1.QModify.ExecQuery;
end;

Select query
  Select * from "SPECTRA"
   where  "Flag"  is not null

Modify query
  update "SPECTRA"
     SET
    "X0"=190
   where  "Flag"  is not null 
     and "WHICH" = 'NSF-0005-13'

CREATE DOMAIN "Domain_ShortString_IDs"    As VARCHAR(5) ;  / * generic IDs * /
CREATE DOMAIN "Domain_Short_Descriptions" AS VARCHAR(50);  / * Name and Type in LU tables * /

CREATE TABLE "Data_Type_LU" (
  "Data_Type_ID"   "Domain_ShortString_IDs" NOT NULL,
  "Data_Type_Text" "Domain_Short_Descriptions",
  "Comment"         VARCHAR(200)
);


  /* deletes all the records in the table */
Delete From "Data_Type_LU" ;

Delete From "Data_Type_LU"
 where "Data_Type_ID" = 'IR'
;

insert into "Data_Type_LU" ("Data_Type_ID", "Data_Type_Text", "Comment") values
('IR', 'IR Spectra','This data is stored as a JCAMP file');


UPDATE "Data_Type_LU" SET "Data_Type_Text"='IR Spectra', "Comment"='New comment' 
 WHERE ("Data_Type_ID"= 'IR')

  /* increments the generator, use 0 to just read it */
SELECT GEN_ID ( "Generator_Name", 1 ) FROM RDB$DATABASE

URL: http:// cpcug.org / user / clemenzi / technical / Databases / Delphi / Firebird / SQL.html