SQL Server 2017

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CREATE TABLE foo ( a int );
INSERT INTO foo VALUES (1),(2),(3);
3 rows affected

ALTER TABLE foo ADD b varchar;
UPDATE foo SET b = CAST( a AS varchar );
ALTER TABLE foo DROP COLUMN a;
Msg 207 Level 16 State 1 Line 2
Invalid column name 'b'.

SELECT * FROM foo;


a


1

2

3