Question

我需要修改以下SQL，以便为名为planogram

的表中设置类别为“beer”的项目检索TTFF数据

select p.product_name, count(t.product_id), avg(t.TTFF), std(t.TTFF)
from product p left join
     TTFFdata t
     on p.product_id = t.product_id
where planogram_id = 1 group by p.product_name

然而，产品没有类别数据，所以我需要以某种方式从货架图表中的类别中获取。像这样的东西，但通过适当的连接使它工作：

select p.product_name, count(t.product_id), avg(t.TTFF), std(t.TTFF)
from product p left join
     TTFFdata t
     on p.product_id = t.product_id
where planogram.category = "beer" group by p.product_name

需要考虑两件事：

我对SQL没有太多体验。

我认为我收到的数据库结构很糟糕（产品没有类别ID？！），但我可能不得不按原样使用它。

任何帮助都非常感激。

我正在使用的完整sql如下：

-- phpMyAdmin SQL Dump
-- version 4.6.5.2
-- https://www.phpmyadmin.net/
--
-- Host: localhost
-- Generation Time: Mar 08, 2017 at 07:50 PM
-- Server version: 10.1.21-MariaDB
-- PHP Version: 5.6.30

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";


/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8mb4 */;

--
-- Database: `chart`
--

-- --------------------------------------------------------

--
-- Table structure for table `planogram`
--

CREATE TABLE `planogram` (
  `planogram_id` int(11) NOT NULL,
  `planogram_name` varchar(200) NOT NULL,
  `project_name` varchar(200) NOT NULL,
  `category` varchar(45) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

--
-- Dumping data for table `planogram`
--

INSERT INTO `planogram` (`planogram_id`, `planogram_name`, `project_name`, `category`) VALUES
(1, 'planogramA', '', 'beer'),
(2, 'planogramB', '', 'coffee'),
(3, 'planogramC', '', 'coffee'),
(4, 'planogramD', '', 'fruit'),
(5, 'planogramE', '', 'beer');

-- --------------------------------------------------------

--
-- Table structure for table `product`
--

CREATE TABLE `product` (
  `product_id` int(11) NOT NULL,
  `product_name` varchar(200) NOT NULL,
  `detail` varchar(200) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

--
-- Dumping data for table `product`
--

INSERT INTO `product` (`product_id`, `product_name`, `detail`) VALUES
(1, 'beer1', ''),
(2, 'beer2', ''),
(3, 'coffee1', ''),
(4, 'coffee2', ''),
(5, 'coffee3', ''),
(6, 'coffee4', ''),
(7, 'coffee5', ''),
(8, 'coffee6', ''),
(9, 'beer3', ''),
(10, 'beer4', ''),
(13, 'fruit1', ''),
(14, 'fruit2', '');

-- --------------------------------------------------------

--
-- Table structure for table `TTFFdata`
--

CREATE TABLE `TTFFdata` (
  `record_id` int(11) NOT NULL,
  `participant_id` varchar(45) NOT NULL,
  `TTFF` decimal(10,2) NOT NULL,
  `product_id` int(11) NOT NULL,
  `planogram_id` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

--
-- Dumping data for table `TTFFdata`
--

INSERT INTO `TTFFdata` (`record_id`, `participant_id`, `TTFF`, `product_id`, `planogram_id`) VALUES
(1, 'a1', '6.21', 1, 1),
(2, 'a2', '5.70', 1, 1),
(3, 'a3', '6.00', 1, 1),
(4, 'b1', '3.40', 2, 1),
(5, 'b2', '4.30', 2, 1),
(6, 'b3', '6.00', 2, 1),
(7, 'c1', '7.00', 3, 2),
(8, 'c2', '8.00', 3, 2),
(9, 'c3', '5.00', 3, 2),
(10, 'd1', '8.90', 4, 2),
(11, 'd2', '3.00', 4, 2),
(12, 'd3', '4.50', 4, 2),
(15, 'e1', '8.00', 5, 2),
(16, 'e2', '9.00', 5, 2),
(17, 'f1', '5.50', 6, 3),
(18, 'f2', '5.00', 6, 3),
(19, 'g1', '5.20', 7, 3),
(20, 'g2', '3.60', 7, 3),
(21, 'h1', '5.00', 8, 3),
(22, 'h2', '5.10', 8, 3),
(23, 'i1', '6.00', 13, 4),
(24, 'i2', '7.00', 13, 4),
(25, 'j1', '4.00', 14, 4),
(26, 'j2', '6.00', 14, 4),
(27, 'k1', '6.70', 9, 5),
(28, 'k2', '6.10', 9, 5),
(29, 'l1', '3.00', 10, 5),
(30, 'l2', '5.00', 10, 5);

--
-- Indexes for dumped tables
--

--
-- Indexes for table `planogram`
--
ALTER TABLE `planogram`
  ADD PRIMARY KEY (`planogram_id`);

--
-- Indexes for table `product`
--
ALTER TABLE `product`
  ADD PRIMARY KEY (`product_id`);

--
-- Indexes for table `TTFFdata`
--
ALTER TABLE `TTFFdata`
  ADD PRIMARY KEY (`record_id`),
  ADD KEY `product_id` (`product_id`),
  ADD KEY `planogram_id` (`planogram_id`);

--
-- AUTO_INCREMENT for dumped tables
--

--
-- AUTO_INCREMENT for table `planogram`
--
ALTER TABLE `planogram`
  MODIFY `planogram_id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=6;
--
-- AUTO_INCREMENT for table `product`
--
ALTER TABLE `product`
  MODIFY `product_id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=17;
--
-- AUTO_INCREMENT for table `TTFFdata`
--
ALTER TABLE `TTFFdata`
  MODIFY `record_id` int(11) NOT NULL AUTO_INCREMENT, AUTO_INCREMENT=31;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;

Answer 1

您需要在联接中包含所有3个表，并确保在所有相关字段上进行分组以获得正确的输出。根据样本数据，每个产品只与一个货架图相关联，因此我的答案是基于对整个数据都适用的假设：

select p.product_name, count(t.product_id), avg(t.TTFF), std(t.TTFF)
from product p
left join TTFFdata t on p.product_id = t.product_id
left join planogram pl on t.planogram_id=pl.planogram_id
where planogram.category = "beer"
group by p.product_name

MySQL三路加入？

1 个答案: