Oracle alter table structure statement

1. MODIFY a table field: MODIFY the Data Type of a column (generally, the length is limited and there are many restrictions when it is changed to a different type): Syntax: ALTERTABLE table name MODIFY (

1. MODIFY a TABLE field: MODIFY the Data Type of a column (generally limited to the modification length. There are many restrictions when changing to a different type): Syntax: alter table name MODIFY (

1. Modify the table fields:

Modify the Data Type of a column (generally limited to the modification length. There are many restrictions when changing to a different type ):

Syntax: alter table name MODIFY (column name data type );

Eg1: alter table skate_test modify (author number (10, 0 ));

When modifying the column length, you can only change it to a longer length than the existing field actually saves; otherwise, the following error is prompted:

ORA-01441: cannot reduce column length because some values are too large

Eg2: alter table skate_test modify (author varchar2 (10 ))

When modifying the Data Type of a column, the modified column must be empty; otherwise, the following error is prompted:

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

2. Add a column:

Syntax: alter table name ADD (column name data type );

Eg1: alter table skate_test ADD (author NUMBER (38,0) not null );

3. Change the column Name:

Syntax: alter table name rename column current COLUMN name TO new COLUMN name;

Eg1: alter table skate_test rename column author TO authorer_new;

4. delete a column:

Syntax: alter table Name drop column name;

Eg1: alter table skate_test drop column author;

5. Modify the table name:

Syntax: alter table current TABLE name rename to new TABLE name;

Eg1: alter table skate_test rename to test_sakte

6. Add notes to the table:

Syntax: comment on column table name. column name is 'comment content'; // modify the comment of a table column

Eg1: comment on column MOVO_NEW.TEST_SAKTE IS 'comment content'; // modify the table COMMENT