QueryWrapper、LambdaQueryWrapper、QueryChainWrapper、LambdaQueryChainWrapper比较

SELECT id,order_msg FROM my_mysql.order WHERE order_msg = '57x' // x 代表序号

 

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QueryWrapper   QueryWrapper<OrderEntity> queryWrapper = new QueryWrapper<OrderEntity>().select("id","order_msg").eq("order_msg","571"); orderMapper.selectOne(queryWrapper); // SELECT id,order_msg FROM my_mysql.order WHERE (order_msg = '571') 1 2 LambdaQueryWrapper   // LambdaQueryWrapper // queryWrapper.lambda() 可以转换成此种 wrapper LambdaQueryWrapper<OrderEntity> lambdaQueryWrapper = new LambdaQueryWrapper<OrderEntity>().select(OrderEntity::getId, OrderEntity::getOrderMsg).eq(OrderEntity::getOrderMsg,"572"); orderMapper.selectOne(lambdaQueryWrapper); // SELECT id,order_msg FROM my_mysql.order WHERE (order_msg = '572') 1 2 3 QueryChainWrapper   QueryChainWrapper<OrderEntity> queryChainWrapper = new QueryChainWrapper<>(orderMapper).select("id", "order_msg").eq("order_msg","573"); queryChainWrapper.one(); // SELECT id,order_msg FROM my_mysql.order WHERE (order_msg = '573') 1 2 LambdaQueryChainWrapper   LambdaQueryChainWrapper<OrderEntity> lambdaQueryChainWrapper = new LambdaQueryChainWrapper<>(orderMapper).select(OrderEntity::getId, OrderEntity::getOrderMsg).eq(OrderEntity::getOrderMsg,"574"); lambdaQueryChainWrapper.one(); // SELECT id,order_msg FROM my_mysql.order WHERE (order_msg = '574') 1 2 总结 QueryWrapper 和 lambdaQueryWrapper 需要将 封装的wrapper 提供给 orderMapper，调用orderMapper的方法，才可以使用。   QueryChainWrapper 和 LambdaQueryChainWrapper 可以直接链式调用数据执行操作的方法   带 lambda 的 wrapper 可以使用lambda表达式，选择列，设置列值，反之不带lambda的就需要手动指定列名