Ánh xạ kiểu dữ liệu giữa SQLSERVER và Java

8 Mapping SQL data types into Java

8.1     Constraints

We need to provide reasonable Java mappings for the common SQL data types. We also need to make sure that we have enough type information so that we can correctly store and retrieve parameters and recover results from SQL statements. However, there is no particular reason that the Java data type needs to be exactly isomorphic to the SQL data type. For example, since Java has no fixed length arrays, we can represent both fixed length and variable length SQL arrays as variable length Java arrays. We also felt free to use Java Strings even though they don’t precisely match any of the SQL CHAR types.

Table 2 shows the default Java mapping for various common SQL data types. Not all of these types will necessarily be supported by all databases. The various mappings are described more fully in the following sections.