Test Column exists, Add Column, and Update Column

Question

I\'m trying to write a SQL Server database update script. I want to test for the existence of a column in a table, then if it doesn\'t exist add the column with a default va

Answer 1

I have often been annoyed by this problem myself, and unfortunately the solution suggested in Aaronaught's answer quickly becomes messy when @parameters and 'strings' are involved. However, I have found a different workaround by exploiting the usage of synonyms:

IF(COL_LENGTH('MyTable', 'NewCol') IS NULL)
BEGIN
    ALTER TABLE MyTable ADD NewCol VARCHAR(16) NULL;

    CREATE SYNONYM hack FOR MyTable;
    UPDATE hack SET NewCol = 'Hello ' + OldCol;
    DROP SYNONYM hack;

    ALTER TABLE MyTable ALTER COLUMN NewCol VARCHAR(16) NOT NULL;
END