how to change existing data type in sql code example

Example 1: sql server alter column

ALTER TABLE table_name 
ALTER COLUMN column_name new_data_type(size);

Example 2: sql alter column

Changes the data type of a table’s column.
Example: In the ‘users’ table, make the column ‘incept_date’ into a
‘datetime’ type.
ALTER TABLE users
ALTER COLUMN incept_date datetime;