如何在 MySQL 中加入多个表？

Question

The image of the table relation can be found at image .

-- Table structure for table `area`
CREATE TABLE `area` (
  `area_id` int(10) NOT NULL auto_increment,
  `area_name` varchar(255) NOT NULL,
  PRIMARY KEY  (`area_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;

INSERT INTO `area` (`area_id`, `area_name`) VALUES
(1, 'Area 1'),
(2, 'Area 2'),
(3, 'Area 3'),
(4, 'Area 4');

-- Table structure for table `fruits`


CREATE TABLE `fruits` (
  `fruit_id` int(10) NOT NULL auto_increment,
  `fruit_name` varchar(255) NOT NULL,
  `area_id` int(10) NOT NULL,
  PRIMARY KEY  (`fruit_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=5 ;



INSERT INTO `fruits` (`fruit_id`, `fruit_name`, `area_id`) VALUES
(1, 'Apple', 1),
(2, 'Orange', 1),
(3, 'Mango', 2),
(4, 'Apricot', 3);


-- Table structure for table `vegetables`
CREATE TABLE `vegetables` (
  `veg_id` int(10) NOT NULL auto_increment,
  `veg_name` varchar(255) NOT NULL,
  `area_id` int(10) NOT NULL,
  PRIMARY KEY  (`veg_id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;

INSERT INTO `vegetables` (`veg_id`, `veg_name`, `area_id`) VALUES
(1, 'Chickpea', 1),
(2, 'Drumstick', 4);

If I use the following query I get the output as below

SELECT
    `area`.`area_name` AS AreaName
    ,COUNT(*) AS num
FROM
    `area`
    INNER JOIN `fruits`
        ON (`fruits`.`area_id` = `area`.`area_id`)
    GROUP BY `fruits`.area_id   

UNION ALL

SELECT
    `area`.`area_name` AS AreaName
    ,COUNT(*) AS num
FROM
    `area`

    INNER JOIN `vegetables`  
        ON (`vegetables` .`area_id` = `area`.`area_id`)
    GROUP BY `vegetables`.area_id

AreaName num
Area 1 2
Area 2 1
Area 3 1
Area 1 1
Area 4 1

But I want the output to be like:

it should fetch all the areas which are present in vegetables and fruits and if the area is repeating in either fruits or vegetables it should return the total count of area_id by totalling the count of fruits and vegetables.. so the output will be like below

AreaName num
Area 1 3
Area 2 1
Area 3 1
Area 4 1

Answer 1

You can use a subselect over your query and use SUM() to add the counts for same area

SELECT t.AreaName ,SUM(t.num) num
FROM ( ....) t
GROUP BY t.AreaName

Fiddle Demo