Matt Gantz makes a staggered change:
In a previous post I showed how to use a batching strategy to remove large amounts of data from a table while it is being used. Today I will apply the same technique to another common problem- changing the datatype of a column. A common use of this is to normalize a text column into an integer (that references another table), but could be used to transition to and from any datatype . Many of the considerations in the previous post apply, so I advise you to read it as well before using this technique.
Click through for the process.