Updating a field in sql
If the original value is in the form of a valid Internet Protocol (IP) address (four number triplets separated by a period: nnn.nnn) and the numbers happen to coincide with a Web address, the conversion results in a valid link.
Otherwise, Access appends to the beginning of each value, and the resulting links are not valid.
You cannot use an update query to add new records to a database, or to delete records from a database.
For that reason, you decide to update the Customers table with the data from the Clients table.In some cases, the conversion process might delete some data.For more information about restrictions when you convert data types, see the section Restrictions on data type conversions.As you continue, remember that although the data types for each table field do not have to match, they must be compatible.Access must be able to convert the data in the source table into a type that the destination table can use.