Mysql 将有序列表拆分为多行

Question

我有一个带有“指令”字段(mediumtext)的数据库，其中每个条目都包含有序列表形式的指令段落。目前，在查看时，每个列表项都会通过使用 PHP nl2br 函数调用来显示在新行中。

示例条目:

1. Place the flour, baking powder and a pinch of salt in a bowl and combine. Set aside. 2. Place the butter and sugar in a mixer bowl and cream at high speed until light and creamy, using the paddle attachment. 3. Reduce the mixer to a moderate speed and gradually add the egg until well emulsified. 4. Add the flour mixture and mix until it comes together to form a dough. Remove the dough from the mixing bowl and place between 2 sheets of baking parchment. 5. Roll the dough to a thickness of 5mm. 6. Place in the freezer while preheating the oven to 170°C/340°F. 7. Peel off the parchment and bake the dough until golden. 8. Allow to cool, then store in a sealed container until needed.

正如您所看到的，文本中也有数字。

我想将这个字段拆分到一个单独的表中，其中每个单独的指令列表项都有自己的行和 ID，将其链接到当前项。

有没有办法可以使用 MySQL 拆分现有字段？可以用“Number.”作为分隔符。

Answer 1

您可以使用存储过程来完成此操作。这个假设步骤从 1 开始，按顺序编号，并且所有步骤看起来都像步骤编号，后跟句点、空格，然后是步骤文本(这就是示例数据的样子)。它应该相当容易修改以使用稍微不同的格式。我已使该过程生成步骤的结果集，但是您也可以将 SELECT 更改为 INSERT 以将步骤复制到新表中。

DELIMITER //
DROP PROCEDURE IF EXISTS split_recipe //
CREATE PROCEDURE split_recipe(IN recipe VARCHAR(2048))
BEGIN
  DECLARE step INT DEFAULT 1;
  DECLARE next_step INT DEFAULT step+1;
  DECLARE this_step VARCHAR(256);
  WHILE recipe RLIKE CONCAT('^[[:blank:]]*', step, '[[.period.]]') DO
    -- is there a next step?
    IF recipe RLIKE CONCAT('^[[:blank:]]*', step, '[[.period.]] .*', next_step, '[[.period.]]') THEN
      SET this_step = SUBSTRING_INDEX(SUBSTRING_INDEX(recipe, CONCAT(next_step, '. '), 1), CONCAT(step, '. '), -1);
    ELSE
      SET this_step = SUBSTRING_INDEX(recipe, CONCAT(step, '. '), -1);
    END IF;
    -- output this step
    SELECT step, this_step;
    -- remove this step from the recipe
    SET recipe = SUBSTRING_INDEX(recipe, CONCAT(step, '. ', this_step), -1);
    SET step = next_step;
    SET next_step = step + 1;
  END WHILE;
END //

使用您的示例数据:

CALL split_recipe('1. Place the flour, baking powder and a pinch of salt in a bowl and combine. Set aside. 2. Place the butter and sugar in a mixer bowl and cream at high speed until light and creamy, using the paddle attachment. 3. Reduce the mixer to a moderate speed and gradually add the egg until well emulsified. 4. Add the flour mixture and mix until it comes together to form a dough. Remove the dough from the mixing bowl and place between 2 sheets of baking parchment. 5. Roll the dough to a thickness of 5mm. 6. Place in the freezer while preheating the oven to 170°C/340°F. 7. Peel off the parchment and bake the dough until golden. 8. Allow to cool, then store in a sealed container until needed.')

输出:

step    this_step   
1       Place the flour, baking powder and a pinch of salt in a bowl and combine. Set aside. 
2       Place the butter and sugar in a mixer bowl and cream at high speed until light and creamy, using the paddle attachment. 
3       Reduce the mixer to a moderate speed and gradually add the egg until well emulsified. 
4       Add the flour mixture and mix until it comes together to form a dough. Remove the dough from the mixing bowl and place between 2 sheets of baking parchment. 
5       Roll the dough to a thickness of 5mm. 
6       Place in the freezer while preheating the oven to 170°C/340°F. 
7       Peel off the parchment and bake the dough until golden. 
8       Allow to cool, then store in a sealed container until needed.

请注意，此过程会生成多个单行结果集(每个步骤一个 - 我将它们组合起来以便于上面的阅读)。如果只需要一个结果集，则需要修改过程以将步骤存储到临时表中，然后最后从临时表中获取所有数据。或者，可以在应用程序中使用如下代码(针对 PHP/PDO/MySQL):

$result = $link->query("call split_recipe('1. Place the flour...')");
do {
    if ($result->columnCount()) {
        $row = $result->fetch();
        print_r($row);
    }
} while ($result->nextRowset());

这是该过程的修改版本，它将把表 recipes (RecipeID INT, instructions VARCHAR(2048)) 中的菜谱拆分为一个新表 new_recipes (RecipeID INT, step_num INT) ，指令VARCHAR(256))。

DELIMITER //
DROP PROCEDURE IF EXISTS split_recipes //
CREATE PROCEDURE split_recipes()
BEGIN
  DECLARE rid INT;
  DECLARE recipe VARCHAR(2048);
  DECLARE step INT;
  DECLARE next_step INT;
  DECLARE this_step VARCHAR(256);
  DECLARE finished INT DEFAULT 0;
  DECLARE recipe_cursor CURSOR FOR SELECT RecipeID, Instructions FROM recipes;
  DECLARE CONTINUE HANDLER FOR NOT FOUND SET finished = 1;
  DROP TABLE IF EXISTS new_recipes;
  CREATE TABLE new_recipes (RecipeID INT, step_num INT, Instruction VARCHAR(256));
  OPEN recipe_cursor;
  recipe_loop: LOOP
    FETCH recipe_cursor INTO rid, recipe;
    IF finished = 1 THEN
      LEAVE recipe_loop;
    END IF;
    SET step = 1;
    SET next_step = 2;
    WHILE recipe RLIKE CONCAT('^[[:blank:]]*', step, '[[.period.]]') DO
      -- is there a next step?
      IF recipe RLIKE CONCAT('^[[:blank:]]*', step, '[[.period.]] .*', next_step, '[[.period.]]') THEN
        SET this_step = SUBSTRING_INDEX(SUBSTRING_INDEX(recipe, CONCAT(next_step, '. '), 1), CONCAT(step, '. '), -1);
      ELSE
        SET this_step = SUBSTRING_INDEX(recipe, CONCAT(step, '. '), -1);
      END IF;
      -- insert this step into the new table
      INSERT INTO new_recipes VALUES (rid, step, this_step);
      -- remove this step from the recipe
      SET recipe = SUBSTRING_INDEX(recipe, CONCAT(step, '. ', this_step), -1);
      SET step = next_step;
      SET next_step = step + 1;
    END WHILE;
  END LOOP;
END //