SQL Compare will alter existing tables whenever possible when it deploys database schema, but sometimes the entire table must be dropped and recreated. This involves creating a new table, copying all of the data to the new table, and dropping the old table.

SQL Compare will do this in these circumstances:

• Changing an IDENTITY seed or increment value, or dropping the IDENTITY property from a column
• Adding a column in the middle of a table when the 'force column order' option is enabled 
• When you add, alter or drop PERSISTED computed columns 
• When it's impossible to implicitly cast one data type to another (e.g. DECIMAL to NUMERIC) 
• Changing the filegroup specification for a table
• Changing partitioned columns
• Adding a column that has no default and does not accept NULL values
• Azure: when an ALTER COLUMN will cause a Primary Key or clustered index to be dropped and data exists in the table