SQL-Commands DDL

Question 1

DDL - Data Definition Language

Answer 1

statements are defining database schema

Question 2

Create

Answer 2

Create objects in the database

CREATE TABLE table_name
(column_name data_type,
column_name data_type)

CREATE TABLE table 1
( ID int,
Last_name varchar(25)
)

Question 3

Alter

Answer 3

Alter columns in an existing table

Add
ALTER TABLE table_name
ADD column_name data_type

Delete
ALTER TABLE table_name
DROP COLUMN column_name

Modify
ALTER TABLE table_name
MODIFY column_name data_type

ALTER TABLE table_name
RENAME COLUMN column_name 1 to column name 2

Question 4

Drop

Answer 4

Delete a table

DROP TABLE table_name

Question 5

Truncate

Answer 5

Delete data in the table, but not table itself (架空table)

TRUNCATE TABLE table_name

Question 6

Rename

Answer 6

Rename an object