Java 访问MySQL数据库:Connection con = null;
Statement stmt = null;
ResultSet rs = null;
Class.forName(driver);
con = DriverManager.getConnection(url, user, password);
stmt = con.createStatement();
sqlstr = String.format("SELECT objectId FROM %s WHERE className=59",tableName_1);
rs = stmt.executeQuery(sqlstr);除了用COUNT()判断记录rs为空之外还有什么别的方法?
Statement stmt = null;
ResultSet rs = null;
Class.forName(driver);
con = DriverManager.getConnection(url, user, password);
stmt = con.createStatement();
sqlstr = String.format("SELECT objectId FROM %s WHERE className=59",tableName_1);
rs = stmt.executeQuery(sqlstr);除了用COUNT()判断记录rs为空之外还有什么别的方法?
if exists(select objectId FROM %s WHERE className=59)true 的时候不为空
false 的时候为空