import java.io.FileInputStream;
import java.sql.*;
import java.util.Properties;

public class FkSummary {
    public static void main(String[] args) throws Exception {
        Properties props = new Properties();
        try (FileInputStream in = new FileInputStream(args[0])) { props.load(in); }
        try (Connection conn = DriverManager.getConnection(props.getProperty("url"), props.getProperty("username"), props.getProperty("password"))) {
            System.out.println("== FK count by parent table ==");
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery(
                     "SELECT OBJECT_NAME(parent_object_id) AS tbl, COUNT(*) AS fk_cnt " +
                     "FROM sys.foreign_keys GROUP BY parent_object_id ORDER BY tbl")) {
                while (rs.next()) System.out.printf("%-22s %d%n", rs.getString("tbl"), rs.getInt("fk_cnt"));
            }
            System.out.println("== tables WITH FKs: " + "see above" + " ==");
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT COUNT(DISTINCT parent_object_id) FROM sys.foreign_keys")) {
                rs.next(); System.out.println("tables_with_fk=" + rs.getInt(1));
            }
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery("SELECT COUNT(*) FROM sys.tables")) {
                rs.next(); System.out.println("total_tables=" + rs.getInt(1));
            }
            // self-referencing FKs
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery(
                     "SELECT name FROM sys.foreign_keys WHERE parent_object_id = referenced_object_id")) {
                System.out.println("== self-referencing FKs ==");
                while (rs.next()) System.out.println("  " + rs.getString("name"));
            }
            // composite FKs (more than one column)
            try (Statement st = conn.createStatement();
                 ResultSet rs = st.executeQuery(
                     "SELECT fk.name, COUNT(*) AS cols FROM sys.foreign_keys fk " +
                     "JOIN sys.foreign_key_columns fkc ON fkc.constraint_object_id = fk.object_id " +
                     "GROUP BY fk.name HAVING COUNT(*) > 1")) {
                System.out.println("== composite FKs (multi-column) ==");
                while (rs.next()) System.out.printf("  %s (%d cols)%n", rs.getString("name"), rs.getInt("cols"));
            }
        }
    }
}