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法律研究Java DatabaseMetaData getTypeInfo() 方法及示例
DatabaseMetadata 介面的 getTypeInfo() 方法用於獲取底層資料庫支援的所有資料型別的描述。
此方法返回一個 ResultSet 物件，描述支援的資料型別。此物件包含以下詳細資訊的值（作為列名）：
| 列名 | 資料型別 | 描述 |
|---|---|---|
| TYPE_NAME | 字串 | 資料型別的名稱。 |
| DATA_TYPE | 整數 | 表示此資料型別的整數值。 |
| PRECISION | 整數 | 此資料型別的最大精度。 |
| LITERAL_PREFIX | 字串 | 用於引用字串文字的字首。 |
| LITERAL_SUFFIX | 字串 | 用於引用字串文字的字尾。 |
| CASE_SENSITIVE | 布林值 | 確定此資料型別是否區分大小寫 |
| UNSIGNED_ATTRIBUTE | 布林值 | 確定此資料型別是否為無符號屬性。 |
| FIXED_PREC_SCALE | 布林值 | 確定當前資料型別是否可用作貨幣值。 |
| AUTO_INCREMENT | 布林值 | 確定當前資料型別是否可用於自動遞增。 |
| LOCAL_TYPE_NAME | 字串 | 此資料型別的本地化版本。 |
獲取 DatabaseMetaData 物件：
- 確保您的資料庫正在執行。
- 使用 DriverManager 類的 registerDriver() 方法註冊驅動程式。傳遞與底層資料庫對應的驅動程式類的物件。
- 使用 DriverManager 類的 getConnection() 方法獲取連線物件。將資料庫的 URL、使用者名稱和資料庫使用者的密碼作為字串變數傳遞。
- 使用 Connection 介面的 getMetaData() 方法獲取當前連線的 DatabaseMetaData 物件。
最後，透過呼叫 DatabaseMetaData 介面的 getTypeInfo() 方法，獲取包含支援的資料型別描述的 ResultSet 物件。
以下 JDBC 程式建立與 MySQL 資料庫的連線，並檢索所有資料型別的描述。
示例
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
public class DatabaseMetadata_getTypeInfo {
public static void main(String args[]) throws SQLException {
//Registering the Driver
DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//Getting the connection
String url = "jdbc:mysql:///mydatabase";
Connection con = DriverManager.getConnection(url, "root", "password");
System.out.println("Connection established......");
//Retrieving the meta data object
DatabaseMetaData metaData = con.getMetaData();
//Retrieving the columns in the database
ResultSet info = metaData.getTypeInfo();
//Printing the column name and size
while (info.next()) {
System.out.println("Data type name: "+info.getString("TYPE_NAME"));
System.out.println("Integer value representing this datatype: "+info.getInt("DATA_TYPE"));
System.out.println("Maximum precision of this datatype: "+info.getInt("PRECISION"));
if(info.getBoolean("CASE_SENSITIVE")) {
System.out.println("Current datatype is case sensitive ");
} else {
System.out.println("Current datatype is not case sensitive ");
}
if(info.getBoolean("AUTO_INCREMENT")) {
System.out.println("Current datatype can be used for auto increment");
} else {
System.out.println("Current datatype can not be used for auto increment");
}
System.out.println(" ");
}
}
}輸出
Connection established...... Data type name: BIT Integer value representing this datatype: -7 Maximum precision of this datatype: 1 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: BOOL Integer value representing this datatype: -7 Maximum precision of this datatype: 1 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: TINYINT Integer value representing this datatype: -6 Maximum precision of this datatype: 3 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: TINYINT UNSIGNED Integer value representing this datatype: -6 Maximum precision of this datatype: 3 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: BIGINT Integer value representing this datatype: -5 Maximum precision of this datatype: 19 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: BIGINT UNSIGNED Integer value representing this datatype: -5 Maximum precision of this datatype: 20 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: LONG VARBINARY Integer value representing this datatype: -4 Maximum precision of this datatype: 16777215 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: MEDIUMBLOB Integer value representing this datatype: -4 Maximum precision of this datatype: 16777215 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: LONGBLOB Integer value representing this datatype: -4 Maximum precision of this datatype: 2147483647 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: BLOB Integer value representing this datatype: -4 Maximum precision of this datatype: 65535 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: TINYBLOB Integer value representing this datatype: -4 Maximum precision of this datatype: 255 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: VARBINARY Integer value representing this datatype: -3 Maximum precision of this datatype: 255 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: BINARY Integer value representing this datatype: -2 Maximum precision of this datatype: 255 Current datatype is case sensitive Current datatype can not be used for auto increment Data type name: LONG VARCHAR Integer value representing this datatype: -1 Maximum precision of this datatype: 16777215 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: MEDIUMTEXT Integer value representing this datatype: -1 Maximum precision of this datatype: 16777215 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: LONGTEXT Integer value representing this datatype: -1 Maximum precision of this datatype: 2147483647 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: TEXT Integer value representing this datatype: -1 Maximum precision of this datatype: 65535 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: TINYTEXT Integer value representing this datatype: -1 Maximum precision of this datatype: 255 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: CHAR Integer value representing this datatype: 1 Maximum precision of this datatype: 255 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: NUMERIC Integer value representing this datatype: 2 Maximum precision of this datatype: 65 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: DECIMAL Integer value representing this datatype: 3 Maximum precision of this datatype: 65 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: INTEGER Integer value representing this datatype: 4 Maximum precision of this datatype: 10 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: INTEGER UNSIGNED Integer value representing this datatype: 4 Maximum precision of this datatype: 10 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: INT Integer value representing this datatype: 4 Maximum precision of this datatype: 10 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: INT UNSIGNED Integer value representing this datatype: 4 Maximum precision of this datatype: 10 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: MEDIUMINT Integer value representing this datatype: 4 Maximum precision of this datatype: 7 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: MEDIUMINT UNSIGNED Integer value representing this datatype: 4 Maximum precision of this datatype: 8 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: SMALLINT Integer value representing this datatype: 5 Maximum precision of this datatype: 5 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: SMALLINT UNSIGNED Integer value representing this datatype: 5 Maximum precision of this datatype: 5 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: FLOAT Integer value representing this datatype: 7 Maximum precision of this datatype: 10 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: DOUBLE Integer value representing this datatype: 8 Maximum precision of this datatype: 17 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: DOUBLE PRECISION Integer value representing this datatype: 8 Maximum precision of this datatype: 17 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: REAL Integer value representing this datatype: 8 Maximum precision of this datatype: 17 Current datatype is not case sensitive Current datatype can be used for auto increment Data type name: VARCHAR Integer value representing this datatype: 12 Maximum precision of this datatype: 255 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: ENUM Integer value representing this datatype: 12 Maximum precision of this datatype: 65535 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: SET Integer value representing this datatype: 12 Maximum precision of this datatype: 64 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: DATE Integer value representing this datatype: 91 Maximum precision of this datatype: 0 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: TIME Integer value representing this datatype: 92 Maximum precision of this datatype: 0 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: DATETIME Integer value representing this datatype: 93 Maximum precision of this datatype: 0 Current datatype is not case sensitive Current datatype can not be used for auto increment Data type name: TIMESTAMP Integer value representing this datatype: 93 Maximum precision of this datatype: 0 Current datatype is not case sensitive Current datatype can not be used for auto increment
更新於：2019年7月30日
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