ResultSetMetaData - Learn Java by Examples

How do I use ResultSetMetaData to inspect results?

By I Wayan Saryada in JDBC Last modified: April 3, 2026 0 Comment

ResultSetMetaData lets you inspect the shape of a SQL query result at runtime — for example:

how many columns were returned
each column’s name and label
its SQL type
table/schema info if available
whether values can be null, are auto-incremented, etc.

Basic usage

package org.kodejava.jdbc;

import java.sql.*;

public class MetaDataExample {
    public static void main(String[] args) throws Exception {
        String url = "jdbc:postgresql://localhost:5432/postgres";
        String user = "postgres";
        String password = "postgres";

        try (Connection conn = DriverManager.getConnection(url, user, password);
             PreparedStatement ps = conn.prepareStatement("SELECT id, name, created_at FROM users");
             ResultSet rs = ps.executeQuery()) {

            ResultSetMetaData meta = rs.getMetaData();
            int columnCount = meta.getColumnCount();

            for (int i = 1; i <= columnCount; i++) {
                System.out.println("Column " + i);
                System.out.println("  Name: " + meta.getColumnName(i));
                System.out.println("  Label: " + meta.getColumnLabel(i));
                System.out.println("  Type: " + meta.getColumnTypeName(i));
                System.out.println("  Java Type: " + meta.getColumnClassName(i));
                System.out.println("  Table: " + meta.getTableName(i));
                System.out.println("  Nullable: " + meta.isNullable(i));
                System.out.println("  Auto Increment: " + meta.isAutoIncrement(i));
            }
        }
    }
}

Common methods

getColumnCount() — number of columns
getColumnName(i) — actual database column name
getColumnLabel(i) — alias from SQL, if present
getColumnType(i) — JDBC type constant
getColumnTypeName(i) — database-specific type name
getColumnClassName(i) — Java class typically used
getTableName(i) — table name, if the driver provides it
isNullable(i) — whether the column may contain NULL
isAutoIncrement(i) — whether it’s auto-generated
getPrecision(i) / getScale(i) — numeric size details
isReadOnly(i) — whether the column is read-only

Important note: names vs labels

If your query uses aliases:

SELECT first_name AS name FROM users

Then:

getColumnName(1) may return first_name
getColumnLabel(1) returns name

If you want what the query “shows” to the user, prefer getColumnLabel().

Example: print a result set dynamically

try (ResultSet rs = ps.executeQuery()) {
    ResultSetMetaData meta = rs.getMetaData();
    int cols = meta.getColumnCount();

    while (rs.next()) {
        for (int i = 1; i <= cols; i++) {
            String label = meta.getColumnLabel(i);
            Object value = rs.getObject(i);
            System.out.println(label + " = " + value);
        }
        System.out.println("---");
    }
}

Why this is useful

Use ResultSetMetaData when:

you don’t know the query columns in advance
you’re building a generic table printer/exporter
you need to map query results dynamically
you’re debugging SQL joins or aliases

How do I get column’s precision and scale value?

By I Wayan Saryada in JDBC Last modified: May 31, 2024 0 Comment

For instance, you have a number or double typed column in a database table, and you want to get the precision and the scale of that column. Here is an example for you.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

public class ScaleAndPrecisionExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            String query = "SELECT id, quantity, price FROM purchase_order_detail";
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(query);

            ResultSetMetaData metadata = resultSet.getMetaData();
            int precision = metadata.getPrecision(3);
            int scale = metadata.getScale(3);

            System.out.println("Precision: " + precision);
            System.out.println("Scale    : " + scale);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

The result:

Precision: 10
Scale    : 2

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

How do I know the designated column’s table name?

By I Wayan Saryada in JDBC Last modified: May 31, 2024 0 Comment

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

public class TableNameOfColumnExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            String query = """
                    SELECT a.id, a.quantity, a.price, c.name
                    FROM purchase_order_detail a
                    LEFT JOIN purchase_order b ON a.order_id = b.id
                    LEFT JOIN product c on a.product_id = c.id
                    """;

            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(query);

            // Here we have a query that use multiple table, we then want
            // to know to which table a column belongs to. In the
            // ResultSetMetaData there is a getTableName() method that can
            // do this functionality.
            ResultSetMetaData metadata = resultSet.getMetaData();

            String tableName = metadata.getTableName(1);
            System.out.println("Table name of column `a.id` = " + tableName);

            tableName = metadata.getTableName(4);
            System.out.println("Table name of column `c.name` = " + tableName);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

The output of the code snippet above is:

Table name of column `a.id` = purchase_order_detail
Table name of column `c.name` = products

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

How do I know if a table column can have a null value or not?

By I Wayan Saryada in JDBC Last modified: May 31, 2024 0 Comment

In this example we’ll show how to use ResultSetMetaData.isNullable() method to know if a column can be null or not. This method returns an integer which values defined in the constants of ResultSetMetaData.columnNullable, ResultSetMetaData.columnNoNulls and ResultSetMetaData.columnNullableUnknown.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;

public class IsNullableExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(
                    "SELECT id, isbn, title, published_year, price FROM book");

            int columnIndex = 2;
            // The ResultSetMetaData is where all metadata related
            // information for a result set is stored.
            ResultSetMetaData metadata = resultSet.getMetaData();
            String columnName = metadata.getColumnName(columnIndex);
            int nullable = metadata.isNullable(columnIndex);

            // Check the nullable status of a column (`isbn`)
            if (nullable == ResultSetMetaData.columnNullable) {
                System.out.printf("`%s` can have a null value.%n", columnName);
            } else if (nullable == ResultSetMetaData.columnNoNulls) {
                System.out.printf("`%s` does not allowed to have a " +
                                  "null value.%n", columnName);
            } else if (nullable == ResultSetMetaData.columnNullableUnknown) {
                System.out.println("Nullability unknown.");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

How do I know if a table column value is auto-increment?

By I Wayan Saryada in JDBC Last modified: May 31, 2024 0 Comment

The ResultSetMetaData.isAutoIncrement() method can tell us if a column value is automatically numbered or not. This method return true when the column is an auto-increment column, otherwise it returns false. See the example below where we check if the first column (id) is an auto-increment column.

package org.kodejava.jdbc;

import java.sql.*;

public class IsAutoIncrementExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(
                    "SELECT id, username, order_date FROM purchase_order");

            // The ResultSetMetaData is where all metadata related
            // information for a result set is stored.
            ResultSetMetaData metadata = resultSet.getMetaData();
            if (metadata.isAutoIncrement(1)) {
                System.out.println("Column `id` is an auto-increment column.");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>