how to change column data in sql server code example

Example 1: sql change column in existing table

'This adds 'NOT NULL' to excisting column counting in the table mytable'
ALTER TABLE mytable ALTER COLUMN counting INT NOT NULL;

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;