content: package com.alibaba.druid.bvt.sql.mysql.issues;
  
  import com.alibaba.druid.DbType;
  import com.alibaba.druid.sql.SQLUtils;
  import com.alibaba.druid.sql.ast.SQLStatement;
  import com.alibaba.druid.sql.parser.SQLParserUtils;
  import com.alibaba.druid.sql.parser.SQLStatementParser;
  import com.alibaba.druid.sql.visitor.SchemaStatVisitor;
  import com.alibaba.druid.stat.TableStat;
  import com.alibaba.druid.stat.TableStat.Name;
  import org.junit.Test;
  
  import java.util.Map;
  
  import static org.junit.Assert.assertFalse;
  import static org.junit.Assert.assertTrue;
  
  /**
   * 验证 natural join 语句的解析
   *
   * @author lizongbo
   * @see <a href="https://github.com/alibaba/druid/issues/5260">Issue来源</a>
   * @see <a href="https://dev.mysql.com/doc/refman/8.0/en/join.html">MySQL join语法</a>
   */
  public class Issue5260 {
      @Test
      public void test_natural_join() throws Exception {
          for (DbType dbType : new DbType[]{DbType.mysql, DbType.oracle}) {
              for (String sql : new String[]{
                  "select * from t_a natural join t_b;",
                  "SELECT * FROM t1 NATURAL JOIN t2;",
                  "SELECT * FROM t1 NATURAL LEFT JOIN t2;",
                  "SELECT * FROM t1 NATURAL RIGHT JOIN t2;",
                  "SELECT * FROM t1 NATURAL INNER JOIN t2;",
              }) {
                  SQLStatementParser parser = SQLParserUtils.createSQLStatementParser(sql, dbType);
                  SQLStatement statement = parser.parseStatement();
                  System.out.println(dbType + "原始的sql===" + sql);
                  System.out.println(dbType + "归一化的sql===" + Issue5421.normalizeSql(sql));
                  String newSql = statement.toString() + ";";
                  System.out.println(dbType + "生成的sql归一化===" + Issue5421.normalizeSql(newSql));
                  parser = SQLParserUtils.createSQLStatementParser(newSql, dbType);
                  statement = parser.parseStatement();
                  String sqlNew2 = Issue5421.normalizeSql(statement.toString());
                  System.out.println(dbType + "再次解析对象得到sql===" + sqlNew2);
                  System.out.println(dbType + "最原始的实际得到sql===" + Issue5421.normalizeSql(sql));
                  assertTrue(Issue5421.normalizeSql(sql).equalsIgnoreCase(sqlNew2));
                  SchemaStatVisitor visitor = SQLUtils.createSchemaStatVisitor(dbType);
                  statement.accept(visitor);
                  System.out.println("getTables==" + visitor.getTables());
                  Map<Name, TableStat> tableMap = visitor.getTables();
                  assertFalse(tableMap.isEmpty());
              }
          }
      }
  }
  