How do I retrieve available catalogs in database?

By Wayan in JDBC 0 Comment

The examples below show you how to get the available catalog names in MySQL database. The available catalog names can be obtained from the DatabaseMetaData object by calling the getCatalogs() method. This method returns a ResultSet object. We iterate it and get the schema name by calling the getString() method and pass TABLE_CAT as the column name.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

public class MetadataGetCatalog {
    private static final String URL = "jdbc:mysql://localhost";
    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)) {

            // Gets DatabaseMetaData
            DatabaseMetaData metadata = connection.getMetaData();

            // Retrieves the schema names available in this database
            ResultSet rs = metadata.getCatalogs();

            while (rs.next()) {
                String catalog = rs.getString("TABLE_CAT");
                System.out.println("Catalog: " + catalog);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Here is the list of catalog names available in the MySQL database:

Catalog: kodejava
Catalog: musicdb
Catalog: mysql
Catalog: performance_schema
Catalog: sys

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.1.0</version>
</dependency>

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How do I get the maximum number of concurrent connections?

By Wayan in JDBC 0 Comment

This example shows you how to get the maximum number of concurrent connections to a database that are possible.
To get this information, we use the DatabaseMetaData.getMaxConnections() method call. If the return value is zero, it means that there is no limit or the limit is unknown.

package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;
import java.sql.DriverManager;

public class MaxConnections {
    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)) {

            // Get database meta data.
            DatabaseMetaData metaData = connection.getMetaData();

            // Retrieves the maximum number of concurrent
            // connections to this database that are possible.
            // A result of zero means that there is no limit or
            // the limit is not known.
            int max = metaData.getMaxConnections();
            System.out.println("Max concurrent connections: " + max);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

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

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How do I get system functions supported by database?

By Wayan in JDBC 0 Comment 
package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;

public class SystemFunction {
    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)) {
            DatabaseMetaData meta = connection.getMetaData();

            // Get system functions supported by database
            String[] functions = meta.getSystemFunctions().split(",\\s*");

            for (String function : functions) {
                System.out.println("Function = " + function);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Here are MySQL database supported system functions.

Function = DATABASE
Function = USER
Function = SYSTEM_USER
Function = SESSION_USER
Function = PASSWORD
Function = ENCRYPT
Function = LAST_INSERT_ID
Function = VERSION

Maven Dependencies

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

Maven Central

How do I get date time functions supported by database?

By Wayan in JDBC 0 Comment 
package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;

public class DateTimeFunction {
    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)) {
            DatabaseMetaData meta = connection.getMetaData();

            // Get date and time functions supported by database
            String[] functions = meta.getTimeDateFunctions().split(",\\s*");

            for (String function : functions) {
                System.out.println("Function = " + function);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Date and time functions supported by MySQL database.

Function = DAYOFWEEK
Function = WEEKDAY
Function = DAYOFMONTH
Function = DAYOFYEAR
Function = MONTH
Function = DAYNAME
Function = MONTHNAME
Function = QUARTER
Function = WEEK
Function = YEAR
Function = HOUR
Function = MINUTE
Function = SECOND
Function = PERIOD_ADD
Function = PERIOD_DIFF
Function = TO_DAYS
Function = FROM_DAYS
Function = DATE_FORMAT
Function = TIME_FORMAT
Function = CURDATE
Function = CURRENT_DATE
Function = CURTIME
Function = CURRENT_TIME
Function = NOW
Function = SYSDATE
Function = CURRENT_TIMESTAMP
Function = UNIX_TIMESTAMP
Function = FROM_UNIXTIME
Function = SEC_TO_TIME
Function = TIME_TO_SEC

Maven Dependencies

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

Maven Central

How do I get numeric functions supported by database?

By Wayan in JDBC 0 Comment 
package org.kodejava.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;

public class NumericFunction {
    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)) {
            DatabaseMetaData meta = connection.getMetaData();

            // Get numeric functions supported by database
            String[] functions = meta.getNumericFunctions().split(",\\s*");

            for (String function : functions) {
                System.out.println("Function = " + function);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

Here are the numeric functions supported by MySQL database.

Function = ABS
Function = ACOS
Function = ASIN
Function = ATAN
Function = ATAN2
Function = BIT_COUNT
Function = CEILING
Function = COS
Function = COT
Function = DEGREES
Function = EXP
Function = FLOOR
Function = LOG
Function = LOG10
Function = MAX
Function = MIN
Function = MOD
Function = PI
Function = POW
Function = POWER
Function = RADIANS
Function = RAND
Function = ROUND
Function = SIN
Function = SQRT
Function = TAN
Function = TRUNCATE

Maven Dependencies

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

Maven Central