在“商品”条件和[此列中至少有一个值]中显示列

Question

我的桌子上有很多不同的列，例如

resolution, brightness, type, width, camera_type, projection_type etc 

我只需要获取与诸如LED电视之类的过滤器相关的那些列的名称，这意味着我需要某种方式

SHOW COLUMNS FROM Goods WHERE category_id = 5 AND [there is at least one value in the column for a row that meets the category_id = 5 condition]

可能吗

Answer 1

您可以在要获取的行上放置条件，where子句对此负责。 所需的列仅在select语句中指定，无法指定要选择的列。 获得结果后，您可以根据值决定使用哪些列。

Answer 2

我猜你想要的是具有category_id = 5的非空值的列名。这里的困难是找出哪些类别具有category_id = 5的非空值。这必须在一个每列，但可以做到。

说实话...我不在MySql中工作，但是我敢肯定您可以按照要求进行任何调整。

-- create a temp table to hold the results
CREATE TEMPORARY TABLE TempTable (columnName varchar(100));  

-- create a bunch of dynamic SQL to insert its name into the temp table when category_id = 5 and its value is not null

DECLARE column_name VARCHAR(100);

DECLARE no_more_rows BOOLEAN;
DECLARE loop_cntr INT DEFAULT 0;
DECLARE num_rows INT DEFAULT 0;

-- Declare the cursor
DECLARE columns_cur CURSOR FOR
  SELECT
      column_name
  FROM information_schema.columns
  WHERE TABLE_NAME = 'Goods';

-- Declare 'handlers' for exceptions
DECLARE CONTINUE HANDLER FOR NOT FOUND
  SET no_more_rows = TRUE;

OPEN columns_cur;
  select FOUND_ROWS() into num_rows;

the_loop: LOOP

  FETCH  columns_cur 
  INTO   column_name;

  IF no_more_rows THEN
      CLOSE columns_cur;
      LEAVE the_loop;
  END IF;

  PREPARE stmt FROM 'IF(EXISTS(SELECT * FROM Goods WHERE ? IS NOT NULL AND catetory_id = 5)) INSERT INTO TempTable (column_name) VALUES ('?');'

  EXECUTE stmt USING @column_name;
  DEALLOCATE PREPARE stmt;

END LOOP the_loop;