how to change data type in sql code example

Example 1: sql change column types

ALTER TABLE table_name
ALTER COLUMN column_name datatype;

-- Example
ALTER TABLE product
ALTER COLUMN description VARCHAR(250);

Example 2: sql add column

ALTER TABLE Customers
ADD Email varchar(255);

Example 3: sql server alter column

ALTER TABLE table_name 
ALTER COLUMN column_name new_data_type(size);

Example 4: sql alter column size

ALTER TABLE table_name
ALTER COLUMN column_name datatype;

Example 5: alter table modify column

-- ORACLE 18c
ALTER TABLE table_name 
MODIFY column_name datatype;

-- Example
ALTER TABLE product
MODIFY description VARCHAR2(500 char);