If you insert a column with a default value to a table that has existing rows, the column default value is not appended to the existing rows. Instead, the default value defined in the column insert statement is written to the SYS_COLUMNS_AUX table.

If an SQL query is targeted at a row that was inserted to the table before the column, the column value is read from the SYS_COLUMNS_AUX table unless the new column value on the row has been changed after it was inserted. Only the original default value is saved in the SYS_COLUMNS_AUX table.

The columns in the SYS_COLUMNS_AUX system table are described in the following table: