content: package com.platform.admin.tool.meta;
  
  /**
   * MySQL数据库 meta信息查询
   *
   * @author AllDataDC
   * @ClassName MySQLDatabaseMeta
   */
  public class MySQLDatabaseMeta extends BaseDatabaseMeta implements DatabaseInterface {
  
      private volatile static MySQLDatabaseMeta single;
  
      public static MySQLDatabaseMeta getInstance() {
          if (single == null) {
              synchronized (MySQLDatabaseMeta.class) {
                  if (single == null) {
                      single = new MySQLDatabaseMeta();
                  }
              }
          }
          return single;
      }
  
      @Override
      public String getSQLQueryComment(String schemaName, String tableName, String columnName) {
          return String.format("SELECT COLUMN_COMMENT FROM information_schema.COLUMNS where TABLE_SCHEMA = '%s' and TABLE_NAME = '%s' and COLUMN_NAME = '%s'", schemaName, tableName, columnName);
      }
  
      @Override
      public String getSQLQueryPrimaryKey() {
          return "select column_name from information_schema.columns where table_schema=? and table_name=? and column_key = 'PRI'";
      }
  
      @Override
      public String getSQLQueryTables() {
          return "show tables";
      }
  
      @Override
      public String getSQLQueryColumns(String... args) {
          return "select column_name from information_schema.columns where table_schema=? and table_name=?";
      }
  }
  