primary-key

How do I rename a primary key column in MySQL? it's no different than altering any other column -- ALTER TABLE `pkey` CHANGE `keyfield` `keyfield2` INT( 11 ) NOT NULL AUTO_INCREMENT this changes the column keyfield in table pkey to be called keyfield2 -- you have to supply the definition afterwards, as usual. Maybe you have a foreign key constraint in place. You can disable those by SET foreign_key_constraints=0 but you have to remember to update the database afterwards. Leave off the PRIMARY KEY part of the alter statement. The primary key will be updated automatically. Possible a bad

What is the difference between Primary key And unique Key constraint ? What's the use of it?? Both are used to denote candidate keys for a table. You can only have one primary key for a table so would just need to pick one if you have multiple candidates. Either can be used in Foreign Key constraints. In SQL Server the Primary Key columns cannot be nullable. Columns used in Unique Key constraints can be. By default in SQL Server the Primary Key will become the clustered index if it is created on a heap but it is by no means mandatory that the PK and clustered index should be the same. A

I am working on the design of a database that will be used to store data that originates from a number of different sources. The instances I am storing are assigned unique IDs by the original sources. Each instance I store should contain information about the source it came from, along with the ID it was associated by this source. As an example, consider the following table that illustrates the problem: ---------------------------------------------------------------- | source_id | id_on_source | data | ---------------------------------------------------------------- | 1 | 17600 | ... | | 1 |

Right now, I have a table whose primary key is an auto_increment field. However, I need to set the primary key as username , date (to ensure that there cannot be a duplicate username with a date). I need the auto_increment field, however, in order to make changes to row information (adding and deleting). What is normally done with this situation? Thanks! Just set a unique index on composite of (username, date). ALTER TABLE `table` ADD UNIQUE INDEX `name` (`username`, `date`); Alternatively, you can try to ALTER TABLE `table` DROP PRIMARY KEY, ADD PRIMARY KEY(`username`,`date`); and I think in

I am inserting many records using JDBC batch inserts. Is there any way to get the generated key for each record? Can I use ps.getGeneratedKeys() with batch inserts? I am using oracle.jdbc.OracleDriver final String insert = "Insert into Student(RollNumber, Name, Age) values(StudentSEQ.nextval, ? , ?)"; final int BATCH_SIZE = 998; int count = 0; Connection con = null; PreparedStatement ps = null; try { con = getConnection(); ps = con.prepareStatement(insert); for (Student s : students) { ps.setString(1, s.getName()); ps.setInt(2, s.getAge()); ps.addBatch(); count++; if (count % BATCH_SIZE == 0)

I had a custom primary key that need to be set up on a particular data in a model. This was not enough, as an attempt to insert a duplicate number succeeded. So now when i replace primary_key=True to unique=True it works properly and rejects duplicate numbers!!. But according this document ( which uses fields ). primary_key=True implies null=False and unique=True. Which makes me confused as in why does it accept the value in the first place with having an inbuilt unique=True ? Thank you. Updated statement: personName = models.CharField(primary_key=True,max_length=20) mipadi Use an AutoField