向具有特定序号位置的 DB2/400 表添加一列

Question

AS400/iSeries/System-i/whatever 上是否有 SQL 命令可以将列添加到表的特定顺序位置，或将现有列移动到不同位置？

Answer 1

IBM i 7.1 现在允许您在另一列之前添加一列。

ALTER TABLE table ADD COLUMN colname ... BEFORE othercolumn

Answer 2

No. The ALTER TABLE statement will allow you add a column to a table, but, according to the documentation:

The new column is the last column of the table; that is, if initially there are n columns, the added column is column n+1.

If you'd like to change the order of columns in your table, your best bet is to:

1. Use the RENAME statement to rename the table.
2. Recreate the table, with its original name, with the columns in the order that you want.
3. Use an INSERT SELECT to populate the new table with the data from the renamed table.
4. When you're sure the data is intact, you can drop the renamed version of the table.