A.7.2. How to Change the Order of Columns in a Table
First, consider whether you really need to change the column
order in a table. The whole point of SQL is to abstract the
application from the data storage format. You should always
specify the order in which you wish to retrieve your data. The
first of the following statements returns columns in the order
col_name1,
col_name2,
col_name3, whereas the second returns
them in the order col_name1,
col_name3,
col_name2:
mysql> SELECT col_name1, col_name2, col_name3 FROM tbl_name;
mysql> SELECT col_name1, col_name3, col_name2 FROM tbl_name;
If you decide to change the order of table columns anyway, you
can do so as follows:
Create a new table with the columns in the new order.
-
Execute this statement:
mysql> INSERT INTO new_table
-> SELECT columns-in-new-order FROM old_table;
Drop or rename old_table.
-
Rename the new table to the original name:
mysql> ALTER TABLE new_table RENAME old_table;
SELECT * is quite suitable for testing
queries. However, in an application, you should
never rely on using SELECT
* and retrieving the columns based on their position.
The order and position in which columns are returned does not
remain the same if you add, move, or delete columns. A simple
change to your table structure could cause your application to
fail.
