MySQL - 如何根据两个不同表之间的关系从表中选择所有结果？

Question

I have three tables: Inquery , Operator and Operator_Region .

The data entered in the tables are as follows:

Each operator can have one or more regions. I need to display all the results of the INQUIRY table that have the Region field equal to the logged-in user's( Operator ) Operator_Region.regionName field. see the image below:

I'm trying as follow:

SELECT region FROM `INQUIRY`
INNER JOIN `OPERATOR` on `INQUIRY`.`region` WHERE `INQUIRY`.`region` IN (

SELECT
    regionName
FROM
    `OperatorRegion`
INNER JOIN `Operator` ON `OperatorRegion`.`OperatorID` = operatorID
WHERE
    operatorRegion.operatorID = 2)

I need that the query to return only the INQUIRY table rows that match to the logged in operator's region (in this case is Alisson). The operator regions are in the "operator region_table".

But returning empty. This is my SQLFiddle

Answer 1

Consider the following:

DROP TABLE IF EXISTS inquiry;

CREATE TABLE inquiry
(inquiry_id SERIAL PRIMARY KEY
,region VARCHAR(12) 
);

INSERT INTO inquiry VALUES
(1,'Hawaii'),
(2,'Hawaii'),
(3,'Paris'),
(4,'New York');

DROP TABLE IF EXISTS operator;

CREATE TABLE operator 
(operator_id SERIAL PRIMARY KEY
,operator_name VARCHAR(12) NOT NULL UNIQUE
);

INSERT INTO operator VALUES
(101,'John'),
(102,'Alisson'),
(103,'Peter');

DROP TABLE IF EXISTS operator_region;

CREATE TABLE operator_region 
(operator_id INT NOT NULL
,region VARCHAR(12) NOT NULL
,PRIMARY KEY (operator_id,region)
);

INSERT INTO operator_region (operator_id,region) 
VALUES (102,'New York'),
       (102,'Los Angeles'),
       (102,'Hawaii'),
       (101,'New York'),
       (103,'Paris');


SELECT i.* 
  FROM inquiry i 
  JOIN operator_region ro 
    ON ro.region = i.region 
  JOIN operator o 
    ON o.operator_id = ro.operator_id 
 WHERE o.operator_name = 'Alisson';
+------------+----------+
| inquiry_id | region   |
+------------+----------+
|          1 | Hawaii   |
|          2 | Hawaii   |
|          4 | New York |
+------------+----------+