I'm trying to add a key from my customer table to my reservation table in oracle.
However I keep getting an error message when I try to run my SQL commands which states 'Customer_ID is an invalid identifier'.
What I am trying to do is first use an alter statement to alter the reservation table.
Then I am adding a foreign key, which is called 'Customer_ID'
Then I enter a references statement, which tells it that I am getting the CUSTOMER_ID attribute from the customer table. However to sql this doesn't make sense at all.
To me, logically it makes sense, I don't see anything wrong with the syntax or structure of the statements. Any sharp eyes/minds to help me on this matter would be greatly appreciated.
the statements used are:
ALTER TABLE reservation
ADD FOREIGN KEY (Customer_ID)
REFERENCES Customer(Customer_ID);
There's nothing wrong with your syntax; I was able to create simple one-column tables with the appropriate names then execute exactly the statement you posted. So I suspect the column CUSTOMER_ID does not exist in one or the other table. Describe the two tables and double-check the column names. Keep in mind that normally column names in Oracle are case-insensitive, but they can be case-sensitive if enclosed in double quotes; this can be a reason for a non-obvious column name mismatch.
Related
I want to create a table with a column that references the name of a sequence I've also created. Ideally, I'd like to have a foreign key constraint that enforces this. I've tried
create table testtable (
sequence_name varchar2(128),
constraint testtableconstr
foreign key (sequence_name)
references user_sequences (sequence_name)
on delete set null
);
but I'm getting a SQL Error: ORA-01031: insufficient privileges. I suspect either this just isn't possible, or I need to add something like on update cascade. What, if anything, can I do to enforce this constraint when I insert rows into this table?
I assume you're trying to build some sort of deployment management system to keep track of your schema objects including sequences.
To do what you ask, you might explore one of the following options:
Run a report after each deployment that compares the values in your table vs. the data dictionary view, and lists any discrepancies.
Create a DDL trigger which does the insert automatically whenever a sequence is created.
Add a trigger to the table which does a query on the sequences view and raises an exception if not found.
I'm somewhat confused at what you are trying to achieve here - a sequence (effectively) only has a single value, the next number to be allocated, not all the values that have been previously allocated.
If you simply want to ensure that an attribute in the relation is populated from the sequence, then a trigger would be the right approach.
im trying to add a new column to my existing table 'Results', and it seems to be very easy but I cant see the mistake.
Here is my code:
SQL> Alter table results add column CAL ENUM('A','B');
ERROR at line 1: ORA-00904: : invalid identifier
What am I missing?
I've read this from w3 and this from java2s but cant see the difference to mine.
Thanks, and sorry for the dumb question.
OK, with an ORA- error I am assuming that this is an oracle database, and not mysql. you have both tags and you are linking to MySQL example, but the error is not a MySQL error.
Assuming that this IS an Oracle DB, then there is no native ENUM data type. You have to do this as follows: First - you add the column with a correctly defined data type, and second you create a constrained list of permitted values on that column as a check constraint.
Alter table results add (cal varchar2(1));
Alter table results add constraint chk_cal CHECK (cal in ('A','B')) ENABLE;
(EDITED to fix brackets in constraint creation line)
The diagram has over 40 tables, most of them have a primary key defined.
For some reason there is this one table, which has a primary key defined, but that's being ignored when I export the model to a DDL script.
This is the "offending" key (even though it's checked it is nowhere to be found on the generated DDL script):
Has anybody had the same problem? Any ideas on how to solve it?
[EDIT] This is where the key is defined:
And this is the DDL preview (yes, the primary key shows up there):
This is what happens if I try to generate the DDL for just that table (primary key still not generated):
I was finally able to identify and reproduce the problem.
It was a simple conflict of constraints.
Table MIEMBROS had a mandatory 1 to n relationship (foreign key) from another table on its primary key column and vice-versa (there was a foreign key on MIEMBROS against the other table's primary key).
This kind of relationship between two tables makes it impossible to add a record to any of them: The insert operation will return an error complaining about the foreign key restriction pointing the other table.
Anyway I realized that one of the relationships was 0 to n so I simply unchecked the "mandatory" checkbox on the foreign key definition and everything went fine.
So, in a nutshell: The Data Modeler "fails" silently if you are defining a mutual relationship (two foreign keys, one on each table against the other table) on non nullable unique columns, by not generating the primary key of one of the tables.
Such an odd behavior, if you ask me!
"This kind of relationship between two tables makes it impossible to add a record to any of them: The insert operation will return an error complaining about the foreign key restriction pointing the other table."
Actually, if you have deferred constraints, this is not impossible. The constraints can be enforced, for example, at commit time rather than immediately at insert time.
From the Data Modeler menu under File, I used Export -> DDL File. The keys appeared in the DDL, then when I went back to the diagram and did DDL Preview, it showed all the missing stuff.
I am maintaining a legacy application and I recently got contacted that people are getting an error message when they try to fill one of our oracle tables. Now, those oracle tables are not in our care, but I still want to try out something to help find the problem.
Anyway, the error message is the following:
java.sql.SQLException: ORA-00001: unique constraint (REO0.PK_TableName) violated :
I know I can find a lot of information online through google and here about this error message. That is not what my question is about.
The question is: the tablename shown here (which I put in bold), is that
the name of the table, or is the
PK_ part added to represent 'primary key' ?
Reason why I ask is: I can't directly get to this database, but somehow I can see all tables in REO0 and I can find one with TableName but not one with *PK_TableName* as the name for a table. So if this PK_ would refer to something like 'primary key' (which the constraint of is violated) then it would make a bit more sense.
PK_tablename is the name of the constraint, and as Alex Poole states in a good comment, it has been specified in the DDL (CREATE TABLE ... (columns, CONSTRAINT PK_tablename PRIMARY KEY(columns...) ), or ALTER TABLE ... ADD CONSTRAINT PK_tablename PRIMARY KEY(columns...) or CREATE UNIQUE INDEX PK_tablename ON ... (columns) for example). When no name has been given, Oracle generates a name which begins with SYS.
Note that usually PK_x suggests a primary key for table x, but your constraint might also be a foreign key constraint or a not null constraint for example.
The following query will tell you all:
SELECT * FROM all_constraints WHERE constraint_name = 'PK_TABLENAME'
I need to insert records into a table that has no primary key using LINQ to SQL. The table is poorly designed; I have NO control over the table structure. The table is comprised of a few varchar fields, a text field, and a timestamp. It is used as an audit trail for other entities.
What is the best way to accomplish the inserts? Could I extend the Linq partial class for this table and add a "fake" key? I'm open to any hack, however kludgey.
LINQ to SQL isn't meant for this task, so don't use it. Just warp the insert into a stored procedure and add the procedure to your data model. If you can't do that, write a normal function with a bit of in-line SQL.
Open your DBML file in the designer, and give the mapping a key, whether your database has one or not. This will solve your problem. Just beware, however, that you can't count on the column being used for identity or anything else if there isn't a genuine key in the database.
I was able to work around this using a composite key.
I had a similar problem with a table containing only two columns: username, role.
This table obviously does not require an identity column. So, I created a composite key with username and role. This enabled me to use LINQ for adding and deleting entries.
You might use the DataContext.ExecuteCommand method to run your own custom insert statement.
Or, you might add a primary key to a column, this will allow the objects to be tracked for inserts/updates/deletes by the datacontext. This will work even if the column isn't really an enforced primary key in the database (how would linq know?). If you're only doing inserts and never re-use a primary key value in the same datacontext, you'll be fine.