How to create a column and copy another column to the newly created

Question

I am trying to perform a simple task, create a new column in a table and immediately try to copy the value of another column in the same table to the new created column, but I got

Invalid column name "COMMENT_TMP". mistake

SQL

Invalid column name "COMMENT_TMP".

ALTER TABLE TASK_COMMENT ADD COMMENT_TMP text; UPDATE TASK_COMMENT SET TASK_COMMENT.COMMENT_TMP = COMMENT; 

Answer 1

First you need to send the ALTER packet to the server before executing UPDATE . Add GO after ALTER statement

Answer 2

Add the batch separator and table name to the update statement.

 ALTER TABLE TASK_COMMENT ADD COMMENT_TMP text; GO UPDATE TASK_COMMENT SET COMMENT_TMP = COMMENT;