key « Table « Java Database Q&A

1. Relational Database (H2, Java): How do I constrain a foreign key to NOT match another foreign key in the same table?

Simple question. Just wondering if this can be done without me having to enforce this constraint manually in my Java code. These two foreign keys (together in the same ...

2. Java code to find unique key of all the table of the database

I m trying to find all the unique key of all the table. And it would be vendor independent. Please help thanks in advance.

3. Java DB - Why can't I create this table with these foreign key constraints?

I am trying to create three tables: Users

  • username
  • userID
  • category
  • categoryID
  • userID (references user table)
  • amount
  • date
  • expenseID
  • categoryID (references category table) NOT WORKING!
  • userID (references user table) NOT WORKING!
Here is the code of my create statements. Everything worked fine until ...

4. Effect of setting primary key constraints on Nested Table

I have a question about setting primary key constraints on Nested Tables. Let say I have a table: CREATE TABLE A(a Integer, b nested_b) NESTED TABLE b STORE AS b_ntbl; Will setting a primary key constraint on nested_b affect every row in table A or will it affect each row separately? In order word, can an object with primary key K ...

6. which way to generate primary key for table ?

I have a complicated multithread database applicaton. I need to generate unique primary key for table. The data type is "Long". Now I am thinking to use system time to act as id. I want to know, except the system time, do we have some options ? The random API has some build-in method ? Thanks

8. problem in creating table with FULLTEXT KEY index

Hi all I am using mysql-4.1.11-nt stable version, now when i try to create a table with the FULLTEXT KEY index it gives an error saying ERROR 1214 (HY000): The used table type doesn't support FULLTEXT indexes. I am relatively new to MySQL could antone tell me what does this mean The table am creating is as follows:-- CREATE TABLE `contact_us` ...

10. to find the primary key of a table

11. can we join 2 diffrent tables in SQL. which does not have a foriegn key?

then when desigining of tables instead of keeping foreign key and making the design complex can we give each table a unique primary key and then link it instead of creating several foreign keys when there are large number of tables. Which design is good? second doubt : suppose we have ID column as a primary key in one table and ...

12. Regarding Foreign Key Restricts when Alter data type in sql table

Dear friends I have a table named as students. It has a foreign key relation ship with some other table. When i alter the data type from integer to BigInt Foreign_Relationship not allowed to alter data type and throws a error like "ALTER TABLE ALTER COLUMN studentID failed because one or more objects access this column". I need help, how can ...

14. difference between foreign key & Join