In SQL Server 2005, I built a trigger that contains a SQL statement that unpivot's some data. Somewhat similar to the following simple example: http://sqlfiddle.com/#!3/cdc1b/1/0. Let's say that the table the trigger is built on is "table1" and it's set run after updates.
Within SSMS whenever I update "table1" everything works fine. Unfortunately, whenever I update "table1" in a proprietary application (which I don't have the source code to), it fails with the message "The type of column conflit with the type of other columns specified in the UNPIVOT list".
After doing a bit of searching I added COLLATE DATABASE_DEFAULT to my cast's in the view without any luck. It was a bit of a long shot because the collation all matched whenever I queried INFORMATION_SCHEMA.COLUMNS.
I then changed the casts from VARCHAR to CHAR and it worked without issue. For obvious reasons, I'd rather use VARCHAR. What is different between a SSMS and application connection? I assume the application isn't using a connection property that SSMS uses.
PS: The database is a bit funky because it does not use NULLs and uses CHAR instead of VARCHAR.
Related
I need to migrate a DDL from Postgres to DB2, but I need that it works the same as in Postgres. There is a table that generates values from a sequence, but the values can also be explicitly given.
Postgres
create sequence hist_id_seq;
create table benchmarksql.history (
hist_id integer not null default nextval('hist_id_seq') primary key,
h_c_id integer,
h_c_d_id integer,
h_c_w_id integer,
h_d_id integer,
h_w_id integer,
h_date timestamp,
h_amount decimal(6,2),
h_data varchar(24)
);
(Look at the sequence call in the hist_id column to define the value of the primary key)
The business logic inserts into the table by explicitly providing an ID, and in other cases, it leaves the database to choose the number.
If I change this in DB2 to a GENERATED ALWAYS it will throw errors because there are some provided values. On the other side, if I create the table with GENERATED BY DEFAULT, DB2 will throw an error when trying to insert with the same value (SQL0803N), because the "internal sequence" does not take into account the already inserted values, and it does not retry with a next value.
And, I do not want to restart the sequence each time a provided ID was inserted.
This is the problem in BenchmarkSQL when trying to port it to DB2: https://sourceforge.net/projects/benchmarksql/ (File sqlTableCreates)
How can I implement the same database logic in DB2 as it does in Postgres (and apparently in Oracle)?
You're operating under a misconception: that sources external to the db get to dictate its internal keys. Ideally/conceptually, autogenerated ids will never need to be seen outside of the db, as conceptually there should be unique natural keys for export or reporting. Still, there are times when applications will need to manage some ids, often when setting up related entities (eg, JPA seems to want to work this way).
However, if you add an id value that you generated from a different source, the db won't be able to manage it. How could it? It's not efficient - for one thing, attempting to do so would do one of the following
Be unsafe in the face of multiple clients (attempt to add duplicate keys)
Serialize access to the table (for a potentially slow query, too)
(This usually shows up when people attempt something like: SELECT MAX(id) + 1, which would require locking the entire table for thread safety, likely including statements that don't even touch that column. If you try to find any "first-unused" id - trying to fill gaps - this gets more complicated and problematic)
Neither is ideal, so it's best to not have the problem in the first place. This is usually done by having id columns be autogenerated, but (as pointed out earlier) there are situations where we may need to know what the id will be before we insert the row into the table. Fortunately, there's a standard SQL object for this, SEQUENCE. This provides a db-managed, thread-safe, fast way to get ids. It appears that in PostgreSQL you can use sequences in the DEFAULT clause for a column, but DB2 doesn't allow it. If you don't want to specify an id every time (it should be autogenerated some of the time), you'll need another way; this is the perfect time to use a BEFORE INSERT trigger;
CREATE TRIGGER Add_Generated_Id NO CASCADE BEFORE INSERT ON benchmarksql.history
NEW AS Incoming_Entity
FOR EACH ROW
WHEN Incoming_Entity.id IS NULL
SET id = NEXTVAL FOR hist_id_seq
(something like this - not tested. You didn't specify where in the project this would belong)
So, if you then add a row with something like:
INSERT INTO benchmarksql.history (hist_id, h_data) VALUES(null, 'a')
or
INSERT INTO benchmarksql.history (h_data) VALUES('a')
an id will be generated and attached automatically. Note that ALL ids added to the table must come from the given sequence (as #mustaccio pointed out, this appears to be true even in PostgreSQL), or any UNIQUE CONSTRAINT on the column will start throwing duplicate-key errors. So any time your application needs an id before inserting a row in the table, you'll need some form of
SELECT NEXT VALUE FOR hist_id_seq
FROM sysibm.sysdummy1
... and that's it, pretty much. This is completely thread and concurrency safe, will not maintain/require long-term locks, nor require serialized access to the table.
I have a stored procedure that has started to fail for no reason. Well there must be one but I can't find it!
This is the process I have followed a number of times before with no problem.
The source server works fine!
I am doing a pg_dump of the database on source server and imported it onto another server - This is fine I can see all the data and do updates.
Then I run a stored procedure on the imported database that does the following on the database which has 2 identical schema's -
For each table in schema1
Truncate table in schema2
INSERT INTO schema2."table" SELECT * FROM schema1."table" WHERE "Status" in ('A','N');
Next
However this gives me an error now when it did not before -
The error is
*** Error ***
ERROR: column "HBA" is of type boolean but expression is of type integer
SQL state: 42804
Hint: You will need to rewrite or cast the expression.
Why am I getting this - The only difference between the last time I followed this procedure and this time is that the table in question now has an extra column added to it so the "HBA" boolean column is not the last field. But then why would it work in original database!
I have tried removing all data, dropping and rebuilding table these all fail.
However if I drop column and adding it back in if works - Is there something about Boolean fields that mean they need to be the last field!
Any help greatly apprieciated.
Using Postgres 9.1
The problem here - tables in different schemas were having different column order.
If you do not explicitly specify column list and order in INSERT INTO table(...) or use SELECT * - you are relying on the column order of the table (and now you see why it is a bad thing).
You were trying to do something like
INSERT INTO schema2.table1(id, bool_column, int_column) -- based on the order of columns in schema2.table1
select id, int_column, bool_column -- based on the order of columns in schema1.table1
from schema1.table1;
And such query caused cast error because column type missmatch.
We have a Companies table in our database with a "Name" varchar column and its size is currently 30 characters. Our seemingly simple task of changing its size to 50 characters has turned into a bit of an issue. When trying to change it and save the changes through Sybase Central we get the following error:
[Sybase][ODBC Driver][SQL Anywhere]Illegal column definition: Name
SQLCODE: -1046
SQLSTATE: 42000
SQL Statement: ALTER TABLE "DBA"."Companies" ALTER "Name" VARCHAR(50)
We've tried various escaping characters around the column thinking it might have something to do with the word "Name" being treated differently internally by Sybase. We have no indexes or constraints on this column and have removed the single trigger that did exist just trying to isolate any potential factors. Further perplexing us, we have a Companies_a table that keeps track of all changes to the Companies table that has nearly the exact same schema including the Name column. We are able to change that column's size without issue which seems to indicate it's not necessarily an issue with the word "Name". I've gone through all the tabs in Sybase Central for this table, and don't see anything special/different about this table or this column.
Googling this issue is difficult as the word "Name" is extremely common. We have workarounds we can do (ie. creating temp column, copying, dropping & recreating the column, copying back) but if possible I'd like to understand exactly what's happening here and why.
I believe our Companies table and this column were likely created in a previous version of ASA. The inline_max column in sys.systabcol was set to null and we could not change it.
Running the following statement set the defaults:
ALTER TABLE "DBA"."Companies" ALTER "Name" inline use default prefix use default;
I was then able to run this statement without error:
ALTER TABLE "DBA"."Companies" ALTER "Name" VARCHAR(50);
Here's where I found the general concept for the fix:
Sybase SqlAnywhere forum thread
ALTER TABLE [tableName]
ALTER [ColumnName] varchar(4000) NULL
I have two tables that have a column named id_user in common. These two tables are created in my Drupal webpage at some point (that I don't know because I didn't created the Netbeans project).
I checked on the internet and found that probably by adding REFERENCES 1sttable (id_user) to the second table, it should copy the value of the 1sttable (that is always created when a new user arrives) to the id_user value of the 2ndtable (that I don't know at which point is created). Is it correct?
If it's not correct I would like to know a way in pgAdmin that could make me synchronize those tables, or at least create both of them in the same moment.
The problem I have is that the new user has a new row on 1sttable automatically as soon as he registers, while to get a new row on 2ndtable it needs some kind of "activation" like inserting all of the data. What I'm looking for is a way that as soon as there is a new row in the 1sttable, it automatically creates the new row on the other table too. I don't know how to make it more clear (English is not my native language).
The solution you gave me seems clear for the question, but the problem is a little bigger: the two tables presents different kinds of variables, and it should be that they are, one in mySQL, with the user data (drupal default for users), then i have 2 in postgresql, both with the same primary key (id_user):
the first has 118 columns, most of them real integer;
the second has 50 columns, with mixed types.
the web application i'm using needs both this column with all the values NOT EMPTY (otherwise i get a NullPointerException) to work, so what i'm searching for is (i think):
when the user register -inserting his email- in drupal, automatically it creates the two fulfilled columns, to make the web automatically works as soon as the email is stored in mysql. Is it possible? Is it well explained?
My environment is:
windows server 2008 enterprise edition
glassfish 2.1
netbeans 6.7.1
drupal 6.17
postgresql 8.4
mysql 5.1.48
pgAdmin is just the GUI. You mean PostgreSQL, the RDBMS.
A foreign key constraint, like you have only enforces that no value can be used, that isn't present in the referenced column. You can use ON UPDATE CASCADE or ON DELETE CASCADE to propagate changes from the referenced column, but you cannot create new rows with it like you describe. You got the wrong tool.
What you describe could be achieved with a trigger. Another, more complex way would be a RULE. Go with a trigger here.
In PostgreSQL you need a trigger function, mostly using plpgsql, and a trigger on a table that makes use of it.
Something like:
CREATE OR REPLACE FUNCTION trg_insert_row_in_tbl2()
RETURNS trigger AS
$func$
BEGIN
INSERT INTO tbl2 (my_id, col1)
VALUES (NEW.my_id, NEW.col1) -- more columns?
RETURN NEW; -- doesn't matter much for AFTER trigger
END
$func$ LANGUAGE plpgsql;
And a trigger AFTER INSERT on tbl1:
CREATE TRIGGER insaft
AFTER INSERT ON tbl1
FOR EACH ROW EXECUTE PROCEDURE trg_insert_row_in_tbl2();
You might want to read about using Drupal hooks to add extra code to be run when a user is registered. Once you know how to use hooks, you can write code (in a module) to insert a corresponding record in the 2nd table. A good candidate hook to use here would be hook_user for Drupal 6 or hook_user_insert for Drupal 7.
The REFERENCES you read about is part of an SQL command to define a foreign key constraint from the second table to the first. This is not strictly necessary to solve your problem, but it can help in keeping your database consistent. I suggest you read up on database structures and constraints if you want to learn more on this topic.
I am mainly from a Sql Server background, and following some issues with getting MySql to work with the Microsoft Sync Framework (namely it does not cater for snapshots), I am having to look into Postgres and try to get that working with the Sync Framework.
The triggers that are needed include a call to function "##DBTS", but I am having trouble finding an equivalent in Postgres for this.
From the microsoft documentation for this it says:
##DBTS returns the current database's last-used timestamp value.
A new timestamp value is generated when a row with a timestamp
column is inserted or updated.
In MySql it was the following:
USE INFORMATION_SCHEMA;
SELECT MAX(UPDATE_TIME) FROM TABLES WHERE UPDATE_TIME < NOW();
Can anyone tell me what this would be in Postgres?
PostgreSQL does not keep track when a table was last modified. So there is no equivalent for SQL Server's ##DBTS nor for MySQL's INFORMATION_SCHEMA.TABLES.UPDATE_TIME.
You also might be interested in this discussion:
http://archives.postgresql.org/pgsql-general/2009-02/msg01171.php
which essentially says: "if you need to know when a table was last modified, you have to add a timestamp column to each table that records that last time the row was updated".