Http://www.cnblogs.com/LDaqiang/articles/1157998.html due to changes in demand, the field type number (8,2) is now changed to char.
The general idea is as follows:
Rename the field name of the type to back up, and then add a field with the same name as the field name of the type you want to change (the original field has been renamed), then update the data, and finally delete the field that renamed the backup.
The following operations are passed in Oracle 10.2.0.1.0.
1.
/* Modify the original field name */
ALTER Table name RENAME COLUMN field name to field name 1;
2./* Add a field with the same name as the original field */
ALTER table name ADD field name VARCHAR2 (30);
3./*
Update the original data to the new field
It is important to note that the data type conversion (unlike MSSQL) must be displayed
*/
UPDATE table name SET field name = CAST (field name 1 as VARCHAR2 (30));
Note that if you want to modify the field and do not lose data that modifies the previous field, be sure to note here
4./* Delete the original backup field */
ALTER Table name DROP COLUMN field name 1; PS: I make up a comment statement on the basis of the author 5.COMMENT on COLUMN table name. Field name is ' comment content ';
Oracle modifies field types with data
