linked by dept_name

 CREATE TABLE users (
    user_id int(20) AUTO_INCREMENT NOT NULL,
    full_name varchar(50),
    telephone varchar(15),
    dept_id int(20),
    dept_name varchar(50),  
    users.dept_id
   PRIMARY KEY (user_id)
  )
 

  CREATE TABLE dept (
    dept_id INT(11) AUTO_INCREMENT NOT NULL,  
    dept_name VARCHAR(50),
    num_employees INT(11),
   PRIMARY KEY (dept_id)
  )

tables are linked by dept_name
want full_name, dept_name, num_employees
LVL 1
rgb192Asked:
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Patrick MatthewsConnect With a Mentor Commented:
>>tables are linked by dept_name

Why on earth would you do that? dept_id is the best foreign key.  Indeed, having dept_name in the users table is a really bad idea.

I recommend:

1) Remove dept_name from users

2) Forget that num_employees column.  Calculate it on demand instead

3) Query:

SELECT u.full_name, d.dept_name, COUNT(u.user_id) AS num_employees
FROM users u INNER JOIN
    dept d ON u.dept_id = d.dept_id
GROUP BY u.full_name, d.dept_name
0
 
sachinpatil10dConnect With a Mentor Commented:
what matthewspatrick says is perfect.
even though you don't want to change your table structure then use can use this
but join in your current table structure in not good as it will slow down the query process.

SELECT u.full_name, d.dept_name, COUNT(u.user_id) AS num_employees
FROM users u INNER JOIN
    dept d ON u.dept_name= d.dept_name
GROUP BY u.full_name, d.dept_name
0
 
Alpesh PatelConnect With a Mentor Assistant ConsultantCommented:
CREATE TABLE users (
    user_id int(20) AUTO_INCREMENT NOT NULL,
    full_name varchar(50),
    telephone varchar(15),
    dept_id int(20), FK (Dept.dept_id)
   PRIMARY KEY (user_id)
  )
 

  CREATE TABLE dept (
    dept_id INT(11) AUTO_INCREMENT NOT NULL,  
    dept_name VARCHAR(50),
    num_employees INT(11),
   PRIMARY KEY (dept_id)
  )


Select full_name, dept_name, count(1) From
Users left outer join dept
on users.dept_id = dept.dept_id
group by full_name, dept_name
0
 
rgb192Author Commented:
thanks
0
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