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Java DatabaseMetaData getPrimaryKeys() method with example
This method retrieves the description of the primary key columns of a table. It accepts 3 parameters −
catalog - A string parameter representing the name of the catalog (database in general) in which the table exists, pass "" to get the description of the primary key columns in tables with no catalog and, pass null if you don't want to use catalog and thus narrow the search.
schema - A String parameter representing the name of the schema of the table, pass "" to get the description of the columns in tables with no schema and, pass null if you don't want to use schema.
table - A String parameter representing the name of the table.
This method returns a ResultSet object describing specified primary key columns. This object holds values for the following details (as column names) −
| Column name | Data type | Description |
|---|---|---|
| TABLE_CAT | String | Catalog of the table. |
| TABLE_SCHEM | String | Catalog of the schema. |
| TABLE_NAME | String | Name of the table. |
| COLUMN_NAME | String | Name of the column. |
| KEY_SEQ | Short | Sequence number a primary key. |
| PK_NAME | String | Name of the primary key. |
To get the description of required primary key columns of a table in the database −
Make sure your database is up and running.
Register the driver using the registerDriver() method of the DriverManager class. Pass an object of the driver class corresponding to the underlying database.
Get the connection object using the getConnection() method of the DriverManager class. Pass the URL the database and, user name, password of a user in the database, as String variables.
Get the DatabaseMetaData object with respect to the current connection using the getMetaData() method of the Connection interface.
Finally, get ResultSet object holding the description of the required primary key columns, by invoking the getPrimaryKeys() method of the DatabaseMetaData interface .
Example
Let us create a table with name cricketers_data in MySQL database using CREATE statement as shown below −
CREATE TABLE cricketers_data( ID INT, First_Name VARCHAR(255), Last_Name VARCHAR(255), Date_Of_Birth date, Place_Of_Birth VARCHAR(255), Country VARCHAR(255), PRIMARY KEY (ID));
As you observe the column named "ID" of the above table is declared as primary key column.
Following JDBC program establishes connection with MySQL database, retrieves the description of the primary key column of the above table.
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
public class DatabaseMetaData_getPrimaryKeys {
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://localhost/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 rs = metaData.getPrimaryKeys("mydatabase", null, "cricketers_data");
//Printing the column name and size
while (rs.next()){
System.out.println("Table name: "+rs.getString("TABLE_NAME"));
System.out.println("Column name: "+rs.getString("COLUMN_NAME"));
System.out.println("Catalog name: "+rs.getString("TABLE_CAT"));
System.out.println("Primary key sequence: "+rs.getString("KEY_SEQ"));
System.out.println("Primary key name: "+rs.getString("PK_NAME"));
System.out.println(" ");
}
}
}Output
Connection established...... Table name: cricketers_data Column name: ID Catalog name: mydatabase Primary key sequence: 1 Primary key name: PRIMARY
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