I wrote this very simple SP in SQL 2008:
Create procedure dbo.GetNextID
(
#TableName nvarchar(50),
#FieldName nvarchar(50)
)
AS
BEGIN
exec('select isnull(max('+#FieldName+'),0)+1 as NewGeneratedID from '+ #TableName);
END
When I execute this procedure in Visual Studio SQL Express and pass a table name and a field name, it works fine. But when I try to add this SP as a query in a QueryTableAdapter in my ADO DataSet, I receive this error before clicking on Finish button:
the max function requires 1 argument(s)
can anyone help me with this?
I guess that VS tries to determine a field list by executing the SP. But as it does not know what to pass to the SP, it uses empty parameters. Now, of course, your select statement fails.
You could try adding the following to your SP:
IF ISNULL(#TableName,'') = '' SET #TableName = '<Name of a test table>';
IF ISNULL(#FieldName,'') = '' SET #FieldName = '<Name of some field>';
Use the names of some field and table that do exist here (for example names that you'd use from your application, too).
Alternatively you could add the following above the exec:
IF (ISNULL(#TableName, '') = '') OR (ISNULL(#FieldName, '') = '')
BEGIN
SELECT -1 AS NewGeneratedId
RETURN 0
END
EDIT
On a side note, I'd like to warn you about concurrency issues that I see coming up from what your code does. If this code is supposed to return a unique ID for a new record in some table, I'd redesign this as follows:
Create a table NumberSeries where each row contains a unique name, a possible range for IDs and the current ID value.
Create a stored procedure that uses UPDATE ... OUTPUT to update the current ID for a number series and retrieve it in one step.
That way you can make sure that creating a new ID is a single operation that does not cause concurrency problems.
Related
I have created very simple function in DB2oC as below, which has one UPDATE sql statement and one SELECT sql statement along with MODIFIES SQL DATA. But still I get the below error, though I have specified MODIFIES SQL DATA. I did GRANT ALL on that TEST table to my user id and also did GRANT EXECUTE ON FUNCTION to my user id on safe side. Can you please help to explain on what could be the issue?
I have simply invoked the function using SELECT statement like below:
SELECT TESTSCHEMA.MAIN_FUNCTION() FROM TABLE(VALUES(1));
SQL Error [38002]: User defined routine "TESTSCHEMA.MAIN_FUNCTION"
(specific name "SQL201211013006981") attempted to modify data but was
not defined as MODIFIES SQL DATA.. SQLCODE=-577, SQLSTATE=38002,
DRIVER=4.27.25
CREATE OR REPLACE FUNCTION MAIN_FUNCTION()
RETURNS VARCHAR(20)
LANGUAGE SQL
MODIFIES SQL DATA
BEGIN
DECLARE val VARCHAR(20);
UPDATE TEST t SET t.CONTENT_TEXT = 'test value' WHERE t.ID = 1;
select CONTENT_TEXT into val from TEST where ID = 1;
return val;
end;
Appreciate your help.
For the modifies SQL data clause , the usage of the function is restricted on Db2-LUW.
These restrictions do not apply for user defined functions that do not modify data.
For your specific example, that UDF will operate when used as the sole expression on the right hand side of an assignment statement in a compound-SQL compiled statemnent.
For example:
create or replace variable my_result varchar(20) default null;
begin
set my_result = main_function();
end#
Consider using stored procedures to modify table contents, instead of user defined functions.
You could avoid using a function, and just use a single "change data statement"
SELECT CONTENT_TEXT
FROM NEW TABLE(
UPDATE TEST t
SET t.CONTENT_TEXT = 'test value'
WHERE t.ID = 1
)
I've narrowed it down to two possibilities - DynamicSQL and using a case statement.
However, I've failed with both of these.
I simply don't understand dynamicSQL, and how I would use it in my case.
This is my attempt using case statements; one of many failed variations.
SELECT column_name,
CASE WHEN column_name = 'address' THEN (**update statement gives syntax error within here**)
END
FROM information_schema.columns
WHERE table_name = 'employees';
As an overview, I'm using Axios to talk to my Node server, which is making calls to my Heroku database using Massivejs.
Maybe this isn't the way to go - so here's my main problem:
I've ran into troubles because the values I'm planning on using as column names are sent to my server as strings. The exact call that I've been trying to use is
update employees
set $1 = $2
where employee_id = $3;
Once again, I'm passing into those using massive.
I get the error back { error: syntax error at or near "'address'"} because my incoming values are strings. My thought process was that the above statement would allow me to use variables because 'address' is encapsulated by quotes.
But alas, my thought process has failed me.
This seems to be close to answering my question, but I can't seem to figure out what to do in my case if using dynamic SQL.
How to use dynamic column names in an UPDATE or SELECT statement in a function?
Thanks in advance.
I will show you a way to do this by using a function.
First we create the employees table :
CREATE TABLE employees(
id BIGSERIAL PRIMARY KEY,
column1 TEXT,
column2 TEXT
);
Next, we create a function that requires three parameters:
columnName - the name of the column that needs to be updated
columnValue - the new value to which the column needs to be updated
employeeId - the id of the employee that will be updated
By using the format function we generate the update query as a string and use the EXECUTE command to execute the query.
Here is the code of the function.
CREATE OR REPLACE FUNCTION update_columns_on_employee(columnName TEXT, columnValue TEXT, employeeId BIGINT)
RETURNS VOID AS
$$
DECLARE update_statement TEXT := format('UPDATE EMPLOYEES SET %s = ''%s'' WHERE id = %L',columnName, columnValue, employeeId);
BEGIN
EXECUTE update_statement;
end;
$$ LANGUAGE plpgsql;
Now, lets insert some data into the employees table
INSERT INTO employees(column1, column2) VALUES ('column1_start_value','column2_start_value');
So now we currently have an employee with an id value of 1 who has 'column1_start_value' value for the column1, and 'column2_start_value' value for column2.
If we want to update the value of column2 from 'column2_start_value' to 'column2_new_value' all we have to do is execute the following call
SELECT * FROM update_columns_on_employee('column2','column2_new_value',1);
I have a stored procedure that performs inserts and updates in the tables. The need to create it was to try to centralize all the scan functions before inserting or updating records. Today the need arose to return the value of the field ID of the table so that my application can locate the registry and perform other stored procedures.
Stored procedure
SET TERM ^ ;
CREATE OR ALTER procedure sp_insupd (
iaction varchar(3),
iusuario varchar(20),
iip varchar(15),
imodulo varchar(30),
ifieldsvalues varchar(2000),
iwhere varchar(1000),
idesclogs varchar(200))
returns (
oid integer)
as
declare variable vdesc varchar(10000);
begin
if (iaction = 'ins') then
begin
vdesc = idesclogs;
/*** the error is on the line below ***/
execute statement 'insert into '||:imodulo||' '||:ifieldsvalues||' returning ID into '||:oid||';';
end else
if (iaction = 'upd') then
begin
execute statement 'select '||:idesclogs||' from '||:imodulo||' where '||:iwhere into :vdesc;
execute statement 'execute procedure SP_CREATE_AUDIT('''||:imodulo||''');';
execute statement 'update '||:imodulo||' set '||:ifieldsvalues||' where '||:iwhere||';';
end
insert into LOGS(USUARIO, IP, MODULO, TIPO, DESCRICAO) values (
:iusuario, :iip, :imodulo, (case :iaction when 'ins' then 1 when 'upd' then 2 end), :vdesc);
end^
SET TERM ; ^
The error in the above line is occurring due to syntax error. The procedure is compiled normally, that is, the error does not happen in the compilation, since the line in question is executed through the "execute statement". When there was no need to return the value of the ID field, the procedure worked normally with the line like this:
...
execute statement 'insert into '||:imodulo||' '||:ifieldsvalues||';';
...
What would be the correct way for the value of the ID field to be stored in the OID variable?
What is REAL VALUE in ifieldsvalues ?
you can not have BOTH
'insert into '||:imodulo||' '||:ifieldsvalues
'update '||:imodulo||' set '||:ifieldsvalues
because methods to specify column names and column values in INSERT and UPDATE statements is fundamentally different!!! You either would have broken update-stmt or broken insert-stmt!
The error in the above line is occurring due to syntax error
This is not enough. Show the real error text, all of it.
It includes the actual command you generate and it seems you had generated it really wrong way.
all the scan functions before inserting or updating records
Move those functions out of the SQL server and into your application server.
Then you would not have to make insert/update in that "strings splicing" way, which is VERY fragile and "SQL injection" friendly. You stepped into the road to hell here.
the error does not happen in the compilation
Exactly. And that is only for starters. You are removing all the safety checks that should had helped you in applications development.
http://searchsoftwarequality.techtarget.com/definition/3-tier-application
https://en.wikipedia.org/wiki/Multitier_architecture#Three-tier_architecture
http://bobby-tables.com
On modern Firebird versions EXECUTE STATEMENT command can have the same INTO clause as PSQL SELECT command.
https://www.firebirdsql.org/file/documentation/reference_manuals/fblangref25-en/html/fblangref25-psql-coding.html#fblangref25-psql-execstmt
Use http://translate.ru to read http://www.firebirdsql.su/doku.php?id=execute_statement
Or just see SQL examples there. Notice, however, those examples all use SELECT dynamic command, not INSERT. So I am not sure it would work that way.
This works in Firebird 2.5 (but not in Firebird 2.1) PSQL blocks.
execute statement 'insert into Z(payload) values(2) returning id' into :i;
To run it from IBExpert/FlameRobin/iSQL interactive shell add that obvious boilerplate:
execute block returns (i integer) as
begin
execute statement 'insert into Z(payload) values(2) returning id' into :i;
suspend;
end
I have a large query in Firebird (which I run using FlameRobin), using a parameter all over the place, but getting the query below to run will do:
SELECT * FROM customers WHERE customerid = 1234;
I want to define 1234 as a variable, say customerID, so that I can easily replace it with something else.
I've learned that I need to put this inside a EXECUTE BLOCK.
EXECUTE BLOCK
AS
DECLARE customerID INT = 1234;
BEGIN
SELECT * FROM customers WHERE customerid = :customerID
END
If of any importance, the error I am getting is Engine Message :
Dynamic SQL Error
SQL error code = -104
Unexpected end of command - line 3, column 26
The problem is that FlameRobin needs to know when a statement ends and the next statement starts. By default it uses the semicolon (;) for this. However an EXECUTE BLOCK is essentially a stored procedure that isn't stored in the database, so it contains PSQL code that also uses the semicolon as a statement separator.
The consequence of this is that you get syntax errors because FlameRobin is sending incomplete statements to the server (that is: it is sending a statement after each ; it encounters).
You need to instruct FlameRobin to use a different statement terminator using SET TERM. Other Firebird query tools (eg isql) require this as well, but it is not actually part of the syntax of Firebird itself!
So you need to execute your code as:
-- Instruct flamerobin to use # as the terminator
SET TERM #;
EXECUTE BLOCK
AS
DECLARE customerID INT = 1234;
BEGIN
SELECT * FROM customers WHERE customerid = :customerID;
END#
-- Restore terminator to ;
SET TERM ;#
However doing this will still result in an error, because this query is invalid for PSQL: A SELECT in a PSQL block requires an INTO clause to map the columns to variables. And to get the values out of the EXECUTE BLOCK returned to FlameRobin you also need to specify a RETURNS clause as described in the documentation of EXECUTE BLOCK:
-- Instruct flamerobin to use # as the terminator
SET TERM #;
EXECUTE BLOCK
RETURNS (col1 INTEGER, col2 VARCHAR(100))
AS
DECLARE customerID INT = 1234;
BEGIN
SELECT col1, col2 FROM customers WHERE customerid = :customerID INTO :col1, :col2;
SUSPEND;
END#
-- Restore terminator to ;
SET TERM ;#
As far as I know the SUSPEND is technically not required here, but Flamerobin will not fetch the returned row if it isn't included.
However the above will not work if the select produces multiple rows. For that you need to use FOR SELECT ... DO combined with a SUSPEND:
-- Instruct flamerobin to use # as the terminator
SET TERM #;
EXECUTE BLOCK
RETURNS (col1 INTEGER, col2 VARCHAR(100))
AS
DECLARE customerID INT = 1234;
BEGIN
FOR SELECT col1, col2 FROM customers WHERE customerid = :customerID INTO :col1, :col2
DO
SUSPEND;
END#
-- Restore terminator to ;
SET TERM ;#
The SUSPEND here returns the row and waits until the caller has fetched that row and then continues with the FOR loop. This way it will iterate over the results.
IMHO this too much effort for parameterization. You might want to consider simply not parametrizing when you use FlameRobin, or use a tool that supports asking for parameter values for the normal parameter placeholders of Firebird (but to be honest I am not sure if there are any).
Well you need a input and return value, ex:
EXECUTE BLOCK (p_customerID integer=?)
returns(col_1 type of column table.id_cv)
as
begin
for
select col_1 from table
where customerID=:p_customerID
into col_1 do
suspend;
end
Delphi as client side:
myquery1.ParamByName('p_customerID ').Value:=1234;
myquery1.Open()
if not myquery1.IsEmpty then
begin
// using returning values
if myquery1.FieldbyName('col_1').AsString='this' then DoThat();
end;
Use this way ever yout need input parameters and/or returning values;
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.