Create table from FieldDef's (SQLDB)
lazarus / 16-Databases

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fpcoder · 2017-05-04 06:34

Is there a way for SQLDB to create a database table from the
TSQLQuery's FieldDefs ?

If I remember right, in Delphi you could call Dataset.CreateTable and
a table with the designed structure will result from the FieldDef
items?

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GAN · 2017-05-04 07:35

In SQLite I use
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i CREATE
TABLE new_table AS  SELECT expressions  FROM existing_tables  [WHERE
conditions];
You could create and then delete and have the same result (I think).

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i CREATE
TABLE table_2 ASSELECT * FROM table_1LIMIT 1; DELETE FROM table_2;

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Thaddy · 2017-05-04 08:04

Since it descents from TCustomBufDataSet you can call CreateDataset
after you have setup the fielddefs.

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fpcoder · 2017-05-04 10:47

@GAN Thanks for the reply. However, there is no table to select from
yet. I want to create the table from scratch first time the
application runs. At the moment I use a TSQLScript to create the
application tables. But it needs to load some text files with the SQL
commands in. So I thought why not replace that and do it in a more RAD
way: Add table definitions to FieldDefs at design time and then just
call CreateTable at runtime. But it seems that similar to CreateTable
is not implemented in SQLDB.

@Thaddy CreateDataset doesn't create tables, does it? It creates the
TField objects from available FieldDefs. I actually just wanted a more
RAD way of creating tables than running a sqlscript. Maybe I should
try implement CreateTables. But I don't see where NOT NULL can be
specified in the FieldDefs.

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Thaddy · 2017-05-04 11:23

Yes, it DOES create the table (actually it can only create one table
at a time, so it is a bit misleadingly named) ... in memory... so you
will have to persist it. It does not create the table on storage
(either on disk or in an actual database).  But that can be solved by
either saving to file or assigning to another dataset.

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sky_khan · 2017-05-04 12:42

Mapping of lazarus field datatype to SQL column datatype would be
database specific. Some of databases, especially old ones might not
support all types.
Still it is not hard building "create table" query if you know which
database you will use. Btw, I think you can use faRequired attribute
in TFieldDef.Attributes for "not null"