I want to execute multiple statements from my data access layer using C# dan IBM's DB2 data provider.
(environment: DB2/AS400 os version: V5R4)
eg in TSQL:
declare varA integer;
select varA= count(*) from tableA;
select * from tableB where col1 <= varA
with SQL server ; I can concatenate those 3 statements into a string
and assign the text to DBCommand.CommandText.
How to execute multiple statements(compound statement) against DB2 database via DBCommand (using IBM DB2 data provider)
I tried using begin and end block but still failed
BEGIN
statement1;
statement2;
statement3;
END
Thank you
I do not think it's possible.
I had already tried something similar some time ago, and the only solution I found is to dynamically create a stored procedure, calling it, and finally delete it.
Related
Currently I'm working on a simple library project using Embarcadero C++Builder 10.3 Community Edition, and Firebird and FlameRobin to create databases.
So far, I need only use simple queries, that were connected to a single database. Therefore, I used TFDConnection and TFDPhysFbDriverLink to connect to a .fdb file. Then, TFDQuery to create SQL commands and TDataSource. It works great.
Unfortunately, now I must join two tables. How do I write this command? I tried this:
SELECT * FROM users_books
join books on
users_books.id_book = books.id
where users_books and books are databases.
I got an error:
SQL error code = -204
Table unknown
BOOKS.
So I think I must connect somehow to these two databases simultaneously. How to do that?
Firebird databases are isolated and don't know about other databases. As a result, it is not possible to join tables across databases with a normal select statement.
What you can do, is use PSQL (Procedural SQL), for example in an EXECUTE BLOCK. You can then use FOR EXECUTE STATEMENT ... ON EXTERNAL to loop over the table in the other database, and then 'manually' join the local table using FOR SELECT (or vice versa).
For example (assuming a table user_books in the remote database, and a table books in the current database):
execute block
returns (book_id integer, book_title varchar(100), username varchar(50))
as
begin
for execute statement 'select book_id, username from user_books'
on external 'users_books' /* may need AS USER and PASSWORD clause as well */
into book_id, username do
begin
for select book_title from books where id = :book_id
into book_title do
begin
suspend;
end
end
end
I'm trying to create a trigger and am getting the error "[Error] PLS-00357: PLS-00357: Table, View Or Sequence reference 'table_data_seq.nextval' not allowed in this context"
I have read a lot of information on the error and cannot find the difference between the PL/SQL that people say works and mine. Below is my code for creating the trigger ( keeping it as basic as possible to get it working ):
create or replace trigger tr_tabData
before insert on table_data
for each row
DECLARE
seq_value int;
begin
select table_data_sq.nextval into seq_value from dual;
end;
Oracle version is 10.2.0.5
As requested here it the script for the sequence:
DROP SEQUENCE DATA_ADMIN.TABLE_DATA_SQ;
CREATE SEQUENCE DATA_ADMIN.TABLE_DATA_SQ
START WITH 1000
MAXVALUE 999999999999999999999999999
MINVALUE 1
NOCYCLE
CACHE 20
NOORDER;
This is not possible before 11g. You can use sequence_name.NEXTVAL in regular assignments from 11g not before that, and that by the following:
select TABLE_DATA_SQ.NEXTVAL into :NEW.YourID from dual;
It turned out that this was a bug with the TOAD version and my Oracle database version. The same code in SQL*Plus and SQL Developer worked as expected.
I'm currently working on modifying a Firebird v. 1.5 database.
The database structure will be modified running queries from a delphi application using interbase components, the problem I'm facing is that I need to run a lot of queries, some of which include creating generators and updating the generator value, the problem is that I need to achieve this in as few queries as possible, but it seems(at least to me) that this is not really possible, what I'm trying to do is the following:
/* this command creates a generator to be used for table TABLENAME */
CREATE GENERATOR GEN_TABLENAME;
So I've created a generator, now I need to set it's value at the current max id from table TABLENAME, like so:
/* one would expect that the following command would work, well it doesn't */
SET GENERATOR GEN_TABLENAME TO (SELECT MAX(ID) FROM TABLENAME);
Now, is there any workaround for this, or am I forced to:
create the generator
get the max id
update the generator value
and repeat process for every table?
I also expected that
SELECT
SELECT MAX(ID) AS ID_TABLENAME_1 FROM TABLENAME_1,
...
SELECT MAX(ID) AS ID_TABLENAME_N FROM TABLENAME_N
would be a workaround to get the max id's from every table in one command, but it doesn't.
Statement
SET GENERATOR GEN_TABLENAME TO (SELECT MAX(ID) FROM TABLENAME);
mixes DDL (SET GENERATOR) and DML (SELECT), AFAIK this is not generally supported and Firebird doesn't support it for sure.
If you can upgrade to the latest version of Firebird then you could use EXECUTE BLOCK and / or EXECUTE STATEMENT to do it all "in one statement" and server side, but with Firebird 1.5 you have to settle for the long way (one statement to get the current max, then another one update the generator).
With the following trick you can set the generator value to the maximum ID value of a table with one SQL statement in Firebird:
SELECT GEN_ID( GEN_TABLENAME,
(SELECT MAX(ID) FROM TABLENAME) - GEN_ID(GEN_TABLENAME, 0)) FROM RDB$DATABASE;
That works, because GEN_ID( <GeneratorName>, <increment>) gets the generator value and increments it by <increment>. This should work in Firebird 1.5 as well as in newer versions.
You could create a stored procedure and call it from Delphi:
create procedure update_generators
as
declare variable max_id integer;
declare variable table_name char(31);
declare variable generator_name char(31);
begin
/* assuming generator naming convention GEN_XXX -> table name XXX */
for select
trim(g.rdb$generator_name),
substring(trim(g.rdb$generator_name) from 5)
from rdb$generators g
where (coalesce(g.rdb$system_flag, 0) = 0)
into
:generator_name,
:table_name
do
begin
/* assuming that the field name is always ID */
execute statement 'select max(id) from ' || :table_name into :max_id;
execute statement 'set generator ' || :generator_name || ' to ' || :max_id;
end
end^
It looks like execute statement is supported by Firebird 1.5 already.
In Firebird 2.0 and later, you could also wrap the code in a execute block and avoid creating a stored procedure.
Currently my development environment is using SQL server express 2008 r2 and VS2010 for my project development.
My question is like this by providing a scenario:
Development goal:
I develop window services something like data mining or data warehousing using .net C#.
That meant I have a two or more database involved.
my senario is like this:
I have a database with a table call SQL_Stored inside provided with a coloum name QueryToExec.
I first idea that get on my mind is written a stored procedure and i tried to came out a stored procedure name Extract_Sources with two parameter passed in thats ID and TableName.
My first step is to select out the sql need to be execute from table SQL_Stored. I tried to get the SQL by using a simple select statement such as:
Select Download_Sql As Query From SQL_Stored
Where ID=#ID AND TableName=#TableName
Is that possible to get the result or is there another way to do so?
My Second step is to excecute the Sql that i get from SQL_Stored Table.Is possible to
to execute the query that select on the following process of this particular stored proc?
Need to create a variable to store the sql ?
Thank you,Appreciate for you all help.Please don't hesitate to voice out my error or mistake because I can learn from it. Thank you.
PS_1:I am sorry for my poor English.
PS_2:I am new to stored procedure.
LiangCk
Try this:
DECLARE #download_sql VARCHAR(MAX)
Select
#download_sql = Download_Sql
From
SQL_Stored
Where
AreaID = #AreaID
AND TableName = #TableName
EXEC (#download_sql)
I'm currently writing some installer script that fires SQL files against different database types depending on the system's configuration (the webapplication supports multiple database server like MySQL, MSSQL and PostgreSQL).
One of those types is PostgreSQL. I'm not fluent with it and I would like to know if it's possible to make a statement into a define/populate SQL file that makes an SQL query conditional to a specific PostgreSQL server version.
How to make an SQL statement conditionally in plain PGSQL so that it is only executed in version 9? The command is:
ALTER DATABASE dbname SET bytea_output='escape';
The version check is to compare the version with 9.
Postgres does have version() function, however there is no major_vesion(). Assuming that output string always includes version number as number(s).number(s).number(s) you could write your own wrapper as:
CREATE OR REPLACE FUNCTION major_version() RETURNS smallint
AS $BODY$
SELECT substring(version() from $$(\d+)\.\d+\.\d+$$)::smallint;
$BODY$ LANGUAGE SQL;
Example:
=> Select major_version();
major_version
---------------
9
(1 row)
However real issue here is that AFAIK you can't execute your commands conditionally in "pure" SQL and best what you can do is to write some stored function like this:
CREATE OR REPLACE FUNCTION conditionalInvoke() RETURNS void
AS $BODY$
BEGIN
IF major_version() = 9 THEN
ALTER DATABASE postgres SET bytea_output='escape';
END IF;
RETURN;
END;
$BODY$ LANGUAGE plpgsql;
I think that you should rather use some scripting language and generate appropriate SQL with it.
Or you could just use
select setting from pg_settings where name = 'server_version'
Or
select setting from pg_settings where name = 'server_version_num'
If you need major version only
select Substr(setting, 1, 1) from pg_settings where name = 'server_version_num'
or
select Substr(setting, 1, strpos(setting, '.')-1) from pg_settings where name = 'server_version'
if you want it to be compatible with two digit versions.
Maybe you could make things dependent on the output of
select version();
(probably you'll have to trim and substring that a bit)
BTW (some) DDL statements may not be issued from within functions; maybe you'll have to escape to shell-programming and here-documents.