Question

我需要能够输出由Rails生成的SQL UPDATES，而不是实际运行它们或保存记录。我将把SQL更新输出到文件中。

有没有办法在Rails中执行此操作，而不使用字符串插值？

是否可以执行以下操作：

<div id="container">
<h1>BMI and Blood Pressure Calculator</h1>

<div id="body">
    <p>This webpage allows users to calculate their BMI and Blood Pressure by entering in their values into the boxes</p>
    </br>           
    <p>Please enter in your details below</p>

<form>
     <br />
     <br />Patient Information
     <br />Height <input type="text" name="height" size="12" maxlength="20">
     <br />Weight <input type="text" name="weight" size="12" maxlength="20">
     <br />
     <br /><input type="reset" value="Clear Form">
     <br /><input type="submit" value="Submit Information">
</form>
</div>

<?php

        $this->input->post('height');
        $this->input->post('weight');

          if ($_GET['submit']) {
          $height = $_GET['height'];
          $weight = $_GET['weight'];
        }
          function bmi($height,$weight) {
            $bmi = $weight/($height*$height);
            return $bmi;
        }

            $bmi = bmi($weight,$height);

              if ($bmi <= 15) {
                $output = "Very severely underweight";

              } else if ($bmi > 15 AND $bmi<=16 ) {
                $output = "Severely underweight";

              } else if ($bmi > 16 AND $bmi<=18.5) {
                $output = "Underweight";

              } else if ($bmi > 18.5 AND $bmi<=25) {
                $output = "Normal";

              } else if ($bmi > 25 AND $bmi<=30) {
                $output = "Overweight";

              } else if ($bmi > 30 AND $bmi<=35) {
                $output = "Obesity class 1";

              } else if ($bmi > 35 AND $num<=40) {
                $output = "Obesity class 2";

              } else if ($bmi > 60) {
                $output = "Obesity class 3";

              echo "Your BMI is " . $bmi . " and you are : ";
              echo "$output";

              }
        ?>

而不是：

p = Post.where (something)

p.some_value = some_new_value

p.to_sql??? # how to generate the update statement

Answer 1

从@ R.F开始。尼尔森并将其包装成一种方法。您可以使用模型调用to_update_sql作为获取SQL的参数。

def to_update_sql(model)
  return '' if model.changes.empty?

  table = Arel::Table.new(model.class.table_name)
  update_manager = Arel::UpdateManager.new(model.class)
  update_manager.set(model.changes.map{|name, (_, val)| [table[name], val] })
                .where(table[:id].eq(model.id))
                .table(table)

  return update_manager.to_sql
end

post = Post.first
post.some_value = xxxx

to_update_sql(post)
# => UPDATE `posts` SET `some_value` = xxx WHERE `posts`.`id` = 1

rails - 获取模型的SQL保存

1 个答案: