一、JDBC之DatabaseMetaData之获取表信息以及列信息
(1) DatabaseMetaData实例的获取
Connection conn = DriverManager.getConnection("DataBase")；
DatabaseMetaData dbmd = Conn.getMetaData();
(2) 获得当前数据库中表的信息
dbmd.getTables（String catalog,String schema,String tableName,String[] types），
该方法带有四个参数，它们表示的含义如下：
String catalog：要获得表所在的编目。Null表示所有编目。
String schema：要获得表所在的模式。Null表示所有模式。
String tableName：指出要返回表名与该参数匹配的那些表，
String types：一个指出返回何种表的数组。
可能的数组项是："TABLE"、"VIEW"、"SYSTEM TABLE"， "GLOBAL TEMPORARY"，"LOCAL TEMPORARY"，"ALIAS"，"SYSNONYM"。
通过getTables（）方法返回的结果集中的每个表都有下面是10字段的描述信息。
1.TABLE_CAT (String) => 表所在的编目(可能为空)
2.TABLE_SCHEM (String) => 表所在的模式(可能为空)
3.TABLE_NAME (String) => 表的名称
4.TABLE_TYPE (String) => 表的类型。
典型的有 "TABLE", "VIEW", "SYSTEM TABLE", "GLOBAL TEMPORARY", "LOCAL TEMPORARY", "ALIAS", "SYNONYM".
5.REMARKS (String) => 解释性的备注
6.TYPE_CAT (String) =>编目类型(may be null)
7.TYPE_SCHEM (String) => 模式类型(may be null)
8.TYPE_NAME (String) => 类型名称(may be null)
9.SELF_REFERENCING_COL_NAME (String) => name of the designated "identifier" column of a typed table (may be null)
10.REF_GENERATION (String) => specifies how values in SELF_REFERENCING_COL_NAME are created.
它的值有："SYSTEM"、"USER"、"DERIVED"，也可能为空。
(3) 获得某个表的列信息
dbmd.getColumns(String catalog,String schama,String tablename,String columnPattern）
通过getColumns（）方法返回的结果集中的每一列都有下面是23个字段段的描述信息。而且在结果集中直接使用下面字段前面的序号即可获取字段值。
1.TABLE_CAT String => table catalog (may be null)
2.TABLE_SCHEM String => table schema (may be null)
3.TABLE_NAME String => table name (表名称)
4.COLUMN_NAME String => column name(列名)
5.DATA_TYPE int => SQL type from java.sql.Types(列的数据类型)
6.TYPE_NAME String => （数据库中的列对应的类型。如DATE,STRING等）
7.COLUMN_SIZE int => column size.
8.BUFFER_LENGTH is not used.
9.DECIMAL_DIGITS int => the number of fractional digits. Null is returned for data types where DECIMAL_DIGITS is not applicable.
10.NUM_PREC_RADIX int => Radix (typically either 10 or 2)
11.NULLABLE int => is NULL allowed.
12.REMARKS String => comment describing column (may be null)
13.COLUMN_DEF String => default value for the column, (may be null)
14.SQL_DATA_TYPE int => unused
15.SQL_DATETIME_SUB int => unused
16.CHAR_OCTET_LENGTH int => for char types the maximum number of bytes in the column
17.ORDINAL_POSITION int => index of column in table (starting at 1)
18.IS_NULLABLE String => ISO rules are used to determine the nullability for a column.
19.SCOPE_CATLOG String => catalog of table that is the scope of a reference attribute (null if DATA_TYPE isn't REF)
20.SCOPE_SCHEMA String => schema of table that is the scope of a reference attribute (null if the DATA_TYPE isn't REF)
21.SCOPE_TABLE String => table name that this the scope of a reference attribure (null if the DATA_TYPE isn't REF)
22.SOURCE_DATA_TYPE short => source type of a distinct type or user-generated Ref type, SQL type from java.sql.Types
23.IS_AUTOINCREMENT String => Indicates whether this column is auto incremented
二、Select类型之获取表中列信息
String sql = "select * from " + "TABLE_NAME";//假设此时有许多表PreparedStatement stmt = null;
try {
stmt = connect.prepareStatement(sql);
ResultSet rs = stmt.executeQuery();
ResultSetMetaData data = rs.getMetaData();
while (rs.next()) {
for (int i = 1; i <= data.getColumnCount(); i++) {
String columnTypeName = data.getColumnTypeName(i);
String columnName = data.getColumnName(i);
}
}
}
} catch (Exception e) {
} finally {
stmt.close();
}*注意在不使用游标时应关闭。