I have 2 columns MyCol and NewCol. MyCol has already been populated, and may have duplicates (it's not the primary key). I need to insert a value y into NewCol at all rows where MyCol = x. I'm stuck here and not sure how to implement this.
This is just an update statement
UPDATE TABLENAME SET NewCol = Y WHERE MyCol = x
Why exactly could you not find this in ANY introduction to SQL - book, article, reference, team-mate etc?