Some ddl statements for Oracle operations

Recently, the program needs to generate DDL statements to modify the database table of the Oracle database. Therefore, I have summarized the situation of modifying the database table of the Oracle database as follows: 1. Add a column: ALTERTAB.

Recently, the program needs to generate DDL statements to modify the database table of the Oracle database. Therefore, I have summarized the situation of modifying the database table of the Oracle database as follows: 1. Add a column: ALTER TAB.

Recently, the program needs to generate DDL statements to modify the database table of the Oracle database. Therefore, I have summarized the situation of modifying the database table of the Oracle database as follows:

1. ADD a column: alter table table_name ADD (column_name VARCHAR2 (33, 2) DEFAULT '2' not null)

2. delete a COLUMN: alter table table_name drop column column_name

3. Modify the Data Type:

Data: ORA-01439: to change the data type, the column to be modified must be empty (empty)

No data: alter table table_name MODIFY (column_name NUMBER (222,2 ))

4. Modify the default value:

Consistent data types: alter table table_name MODIFY (column_name DEFAULT newVlaue)

Inconsistent Data Types: ORA-02262: ORA-932 appears when a type check is performed on the column default expression

5. Modify NULLABLE:

When changing NULL to not null:

Null: ORA-02296: Unable to enable (TABLE_NAME)-null found

NULL value does NOT exist: alter table table_name MODIFY (column_name not null)

When not null is changed to NULL: alter table table_name MODIFY (column_name NULL)

6. Modify the field name:

Name: alter table table_name rename column old_column_name TO new_column_name

Name does not match: ORA-00904: Invalid identifier

7. Modify the table name:

Name: alter table table_name rename to new_table_name;

Invalid name: ORA-00903: Invalid table name

8. Modify the field length:

When there is a length greater than the new value in the data: ORA-01441: the length of the Column cannot be reduced because some values are too large

Qualified: alter table table_name MODIFY (column_name VARCHAR2 (newLength ))

Note: Oracle imposes the following restrictions on table names and field names:

1. It must start with a letter

2. contains letters and numbers, and # $

3. cannot exceed 30 characters