How do I use DatabaseMetaData to get table column details

How do I use DatabaseMetaData to get table column details

In DatabaseMetaData class we have a method getColumns

getColumns

ResultSet getColumns(String catalog,
                     String schemaPattern,
                     String tableNamePattern,
                     String columnNamePattern)
                     throws SQLException

Retrieves a description of table columns available in the specified catalog.Only column descriptions matching the catalog, schema, table and column name criteria are returned. They are ordered by TABLE_CAT,TABLE_SCHEM, TABLE_NAME, and ORDINAL_POSITION.
Each column description has the following columns:

1. TABLE_CAT String => table catalog (may be null)
2. TABLE_SCHEM String => table schema (may be null)
3. TABLE_NAME String => table name
4. COLUMN_NAME String => column name
5. DATA_TYPE int => SQL type from java.sql.Types
6. TYPE_NAME String => Data source dependent type name, for a UDT the type name is fully qualified
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.
    • columnNoNulls - might not allow NULL values
    • columnNullable - definitely allows NULL values
    • columnNullableUnknown - nullability unknown
12. REMARKS String => comment describing column (may be null)
13. COLUMN_DEF String => default value for the column, which should be interpreted as a string when the value is enclosed in single quotes (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.
    • YES --- if the parameter can include NULLs
    • NO --- if the parameter cannot include NULLs
    • empty string --- if the nullability for the parameter is unknown
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 (null if DATA_TYPE isn't DISTINCT or user-generated REF)
23. IS_AUTOINCREMENT String => Indicates whether this column is auto incremented
    • YES --- if the column is auto incremented
    • NO --- if the column is not auto incremented
    • empty string --- if it cannot be determined whether the column is auto incremented parameter is unknown

The COLUMN_SIZE column the specified column size for the given column. For numeric data, this is the maximum precision. For character data, this is the length in characters. For datetime datatypes, this is the length in characters of the String representation (assuming the maximum allowed precision of the fractional seconds component). For binary data, this is the length in bytes. For the ROWID datatype, this is the length in bytes. Null is returned for data types where the column size is not applicable.

Parameters:

catalog - a catalog name; must match the catalog name as it is stored in the database; "" retrieves those without a catalog; null means that the catalog name should not be used to narrow the search

schemaPattern - a schema name pattern; must match the schema name as it is stored in the database; "" retrieves those without a schema; null means that the schema name should not be used to narrow the search

tableNamePattern - a table name pattern; must match the table name as it is stored in the database

columnNamePattern - a column name pattern; must match the column name as it is stored in the database

Returns:

ResultSet - each row is a column description

Throws:

SQLException - if a database access error occurs

See Also:

getSearchStringEscape()

Example program:

package com.javanotes2all.java.db;

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

public class DatabaseMetadataExample {

 private static final String DRIVER = "com.mysql.jdbc.Driver";
    private static final String URL = "jdbc:mysql://localhost/test";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "";
    
    public static void main(String[] args) throws Exception {
        Connection connection = null;
 try {
     Class.forName(DRIVER);
     connection = DriverManager.getConnection(URL, USERNAME, PASSWORD);
     
     DatabaseMetaData metadata = connection.getMetaData();
     // data is database table
     ResultSet resultSet = metadata.getColumns(null, null, "data", null);
     while (resultSet.next()) {
  String name = resultSet.getString("COLUMN_NAME");
  String type = resultSet.getString("TYPE_NAME");
  int size = resultSet.getInt("COLUMN_SIZE");
  String dvalue=resultSet.getString("COLUMN_DEF");
  
  System.out.println("Column name: [" + name + "]; type: [" + type 
      + "]; size: [" + size + "]"+"; defaultvalue:["+dvalue+"];");
     }
 } catch (SQLException e) {
     e.printStackTrace();
 } finally {
     connection.close();
 }
    }

}

OUTPUT:
Column name: [dataid]; type: [INT]; size: [10]; defaultvalue:[null];
Column name: [dataname2]; type: [VARCHAR]; size: [50]; defaultvalue:[aaaa];
Column name: [dataname1]; type: [VARCHAR]; size: [50]; defaultvalue:[aaa];