Question

Hope someone will help me to build this query. I need to get values from database which are belong to one particular user. These are the columns which I need to get.

01. city_name // From city table
02. district_name // From district table
03. category_name // From category table
04. subscription_period // From tutors table
05. date_registered // From tutors table

I have already got values tutor_id, city_id and category_id respectively 1, 53, 5

My address table has city_id column, City table has district_id column, category table has category_id column and tutor table has tutor_id and address_id.

I tried something like this, but this is not working.

SELECT city_name, district_name, category_name, subscription_period AS sp, date_registered AS date
FROM tutors AS t
INNER JOIN district AS d 
INNER JOIN city ON city.district_id = d.district_id
INNER JOIN address ON address.city_id = 50
INNER JOIN category
WHERE t.tutor_id = 1 AND category.category_id= 5

My expecting result should have 1 row as output but this query give me more rows as output

My SQL Tables

CREATE TABLE tutors (
tutor_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
address_id SMALLINT NOT NULL,
tutor_name VARCHAR(80) NOT NULL,
subscription_period SMALLINT NOT NULL,
date_registered TIMESTAMP  NOT NULL DEFAULT CURRENT_TIMESTAMP,
PRIMARY KEY (tutor_id)
); 

CREATE TABLE address (
address_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
address VARCHAR(40) NOT NULL, 
city_id SMALLINT UNSIGNED NOT NULL,
PRIMARY KEY (address_id)
);

CREATE TABLE district(
district_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
district_name VARCHAR(30) NOT NULL, 
PRIMARY KEY (district_id)
);

CREATE TABLE city(
city_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
city_name VARCHAR(30) NOT NULL, 
district_id SMALLINT UNSIGNED NOT NULL,
PRIMARY KEY (city_id)
);

CREATE TABLE category (
category_id SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
category_name VARCHAR(60) NOT NULL, 
PRIMARY KEY (category_id)
);

CREATE TABLE tutor_category(
tutor_id SMALLINT UNSIGNED NOT NULL,
category_id SMALLINT UNSIGNED NOT NULL,
PRIMARY KEY (tutor_id)
);

Answer 1

Try something like this:

SELECT c.city_name, 
       d.district_name, 
       c.category_name, 
       t.subscription_period AS sp, 
       t.date_registered AS date
FROM tutors t
   INNER JOIN address a ON t.address_id = a.address_id 
   INNER JOIN city c ON c.city_id  = a.city_id 
   INNER JOIN district d ON c.district_id = d.district_id 
   INNER JOIN tutor_category tc on t.tutor_id = tc.tutor_id 
   INNER JOIN category cat on tc.category_id = cat.category_id 
WHERE t.tutor_id = 1 AND cat.category_id= 5 AND c.city_id = 50

You need to JOIN on your tables to ensure you only receive the desired results.

If you are receiving duplicate rows that are identical, you are probably doing something wrong or the definitions you provided are not correct (it appears that this is the case indeed). You could “solve” the issue by adding GROUP BY or DISTINCT to your query but that is not the best approach.