I think what you need is an auto increment (primary key) column. When a record is inserted, it will automatically generate the next number in the sequence. Being a primary key, the column must be unique (i.e no two rows can be the same), so you can identify a specify record in the table. When you insert a record, you can run
SELECT LAST_INSERT_ID();
to retrieve the id that was used. The LAST_INSERT_ID is determined on a per connection basis, so you are guaranteed to get the last id that _you_ inserted, even if there are other users inserting records, as long as you do not run another INSERT.
As for 3, you should not worry about how MySQL stores the rows. You should specify an ORDER BY clause in your SELECT statements to get the order in which you want. If you want to know, MySQL stores the rows ascending (1 is first, 2 is second, ...). However, if a record gets deleted from the table, then MySQL will try to re-use the space that once held that row.
Check out the following links: http://www.mysql.com/doc/en/CREATE_TABLE.html http://www.mysql.com/doc/en/example-AUTO_INCREMENT.html
HTH
Matt
At 01:14 PM 12/23/2003, you wrote:
Hi, I am a beginner in using database. And I appreciate your support and help.
When we first create a table,
1. is it possible to create a column that identifies each record that is to be inserted?
2. If we can create this IDENTITY column, how do we create it? Do we set a maximum to the value of this column? Or the value simply increases as the number of records get inserted into the table grows?
3. when we try to insert the first record to this table, does this record go to the first row in the table? And the value of the IDENTITY for this record is 1? When we try to insert the second record to this table, does the second record automatically go to the second row in the table? And the value of the IDENTITY is 2?
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