How to get name and manager name - mysql

How to get name and manager name
+----+-----------+---------+
| id | name | manager |
+----+-----------+---------+
| 1 | bhupendra | 0 |
| 2 | shyam | 1 |
| 3 | ram | 1 |
| 4 | geeta | 2 |
| 5 | sita | 1 |
+----+-----------+---------+
i need result like
+-----------+-----------+
| name | manager |
+-----------+-----------+
| bhupendra | |
| shyam | bhupendra |
| ram | bhupendra |
| geeta | shyam |
| sita | bhupendra |
+-----------+-----------+


You could self-join the id column on the manager column:
SELECT e.name AS name, m.name AS manager
FROM employee e
LEFT JOIN employee m ON m.id = e.manager


You should use the same table twice using alias
select a.name, b.name as manager
from my_table a
left join my_table b on a.manager = b.id


Check this out
with recursive cte (id, name, parent_id) as (
select id,
name,
manager
from employee
union all
select p.id,
p.name,
p.manager
from employee e
inner join cte
on p.manager = cte.id
)
select * from cte;

Related

Correlated subquery display count column

I have the following query which works fine:
SELECT c.cust_id, c.cust_type_cd, c.city, count(*) as `count`
FROM customer c
INNER JOIN account a
ON a.cust_id = c.cust_id
GROUP BY c.cust_id
HAVING `count` = 2;
Result:
+---------+--------------+---------+-------+
| cust_id | cust_type_cd | city | count |
+---------+--------------+---------+-------+
| 2 | I | Woburn | 2 |
| 3 | I | Quincy | 2 |
| 6 | I | Waltham | 2 |
| 8 | I | Salem | 2 |
| 10 | B | Salem | 2 |
+---------+--------------+---------+-------+
I would like to achieve the same result using a correlated subquery. I have not been able to make a "count" column as show above:
SELECT c.cust_id, c.cust_type_cd, c.city
FROM customer c
WHERE 2 = (
SELECT COUNT(*)
FROM account a
WHERE a.cust_id = c.cust_id
);
Result:
+---------+--------------+---------+
| cust_id | cust_type_cd | city |
+---------+--------------+---------+
| 2 | I | Woburn |
| 3 | I | Quincy |
| 6 | I | Waltham |
| 8 | I | Salem |
| 10 | B | Salem |
+---------+--------------+---------+
How can I achieve the same result as the one using the INNER JOIN and have a "count" column?

Not sure why you wanted this but you also need to specify the subquery in the SELECT part,
SELECT c.cust_id, c.cust_type_cd, c.city, (SELECT COUNT(*)
FROM account a
WHERE a.cust_id = c.cust_id) AS `count`
FROM customer c
WHERE 2 = (
SELECT COUNT(*)
FROM account a
WHERE a.cust_id = c.cust_id
);

Why does Apache Drill select column with the same name of a different table

I have a PostgreSQL database linked to a Drill instance.
Whenever I am trying to join 2 tables which both have a column name and whenever I want to select this name Drill selects the wrong name column. What am I doing wrong?
Given the following 2 tables:
Department
| id | name |
|----|------|
| 1 | A |
| 2 | B |
Employee
| id | name | dept | salary |
|----|------|------|--------|
| 1 | U | 1 | 100 |
| 2 | V | 1 | 75 |
| 3 | W | 1 | 120 |
| 4 | X | 2 | 95 |
| 5 | Y | 2 | 140 |
| 6 | Z | 2 | 55 |
Running
select employee.name, employee.salary
from employee
inner join department on employee.dept = department.id
where department.name = 'A'
returns
| name | salary |
|------|--------|
| A | 100 |
| A | 75 |
| A | 120 |
Running
select dept.name, employee.salary
from employee
inner join department on employee.dept = department.id
where department.name = 'A'
returns
| name | salary |
|------|--------|
| null | 100 |
| null | 75 |
| null | 120 |
What does work, but seems very silly to me, is:
select dept.name, employee.salary
from employee
inner join (select id, name as deptname from department) as department on employee.dept = department.id
where department.deptname = 'A'

This seems to be because you use
select dept.name, [...]
But you have never assigned an alias for the table department (department AS dept). Hence
select department.name, [...]
should yield the value you are looking for.

mysql select count from multiple tables

If I have two tables job, employee.
I need to select all from job and append employee count for each job.
Supposed Result
job table
+-------------+-------------+
| id | name |
+-------------+-------------+
| 1 | Teacher |
+-------------+-------------+
| 2 | Engineer |
+-------------+-------------+
| 3 | Programmer |
+-------------+-------------+
employee table
+-------------+-------------+-------------+
| id | name | job_id |
+-------------+-------------+-------------+
| 1 | employee N | 1 |
+-------------+-------------+-------------+
| 2 | employee N | 2 |
+-------------+-------------+-------------+
| 3 | employee N | 3 |
+-------------+-------------+-------------+
| 4 | employee N | 1 |
+-------------+-------------+-------------+
| 5 | employee N | 3 |
+-------------+-------------+-------------+
| 6 | employee N | 1 |
+-------------+-------------+-------------+
I need to select all from job and append employee count for each job.
Supposed Result
Result table
+-------------+-------------+--------------+
| id | name |employee count|
+-------------+-------------+--------------+
| 1 | Teacher | 3 |
+-------------+-------------+--------------+
| 2 | Engineer | 1 |
+-------------+-------------+--------------+
| 3 | Programmer | 2 |
+-------------+-------------+--------------+

I like to use left join : )
SELECT job.id, job.name, count( * ) AS 'employee count'
FROM job
LEFT JOIN employee
ON job.id = employee.job_id
GROUP BY job.id

You want to use INNER JOIN to join the tables, then GROUP BY to group on the job id. Finally use COUNT() to get a count of each group
SELECT job.id, job.name, count(*) AS employee_count
FROM job
INNER JOIN employee
ON job.id = employee.job_id
GROUP BY job.id
You can see it live here http://sqlfiddle.com/#!2/9d59c1/1

How to select table and count other table

Suppose I have two tables:
Customers
Name | id |
-------------------
Benny | 1 |
Wilson | 2 |
Joe | 3 |
Austin | 4 |
Orders
Product | id |
---------------------
TV | 1 |
Hifi-set | 1 |
HTPC | 1 |
CD | 1 |
DVD | 1 |
CD | 1 |
DVD | 1 |
And this is what I want with the results:
Name | Orders |
-------------------
Benny | 7 |
Wilson | 0 |
Joe | 0 |
Austin | 0 |
I'm not familiar with SQL, But I tried:
SELECT c.Name FROM Customers AS c LEFT JOIN Orders AS o ON c.id=o.id GROUP BY c.Name
But got a wrong result:
Name | Orders |
-------------------
Benny | 4 |
Wilson | 1 |
Joe | 1 |
Austin | 1 |
What do I do?

Try:
select
c.Name,
(select count(1) from Orders where ID=c.ID)
from
Customers as c

By not using SubQuery, you can also JOIN instead.
SELECT a.Name, COUNT(b.id)
FROM Customers a LEFT JOIN Orders b
on a.ID = b.ID
GROUP BY a.Name

MySQL UNION with WHERE

I have the following 2 tables
tableA a (id, name, surname, program, date)
tableB b (id, aid, name, surname, extracard)
with tableA.id = tableB.aid (1 to n relationship)
Sample data for tableA:
| ID | NAME | SURNAME | PROGRAM | DATE | EXPIRES |
----------------------------------------------------------
| 1 | TOM | JONES | 1,2,3 | 12/8/2012 | 12/8/2013 |
| 2 | JAMIE | OLIVER | 4,5,6 | 15/8/2012 | 15/8/2013 |
Sample data for tableB:
| ID | AID | NAME | SURNAME | CARD |
-------------------------------------
| 1 | 1 | ANNE | JONES | 1 |
| 2 | 1 | JACK | BOWER | 0 |
| 3 | 2 | KATE | PERRY | 1 |
| 4 | 2 | JOHN | DOE | 0 |
| 5 | 2 | HARRY | POTTER | 0 |
In the results, each member of tableB should have all values (program, date, expires, etc...) from tableA and display only the name, surname from tableB in the same column (coalesce??). Also, I need to use a between clause for a.id between (%id1 and %id2) and also a WHERE statement for selecting rows where tableB.card=1
| a.ID | NAME | SURNAME | PROGRAM | DATE | EXPIRES |
------------------------------------------------------------
| 1 | TOM | JONES | 1,2,3 | 12/8/2012 | 12/8/2013 |
| 1 | ANNE | JONES | 1,2,3 | 12/8/2012 | 12/8/2013 |
| 2 | JAMIE | OLIVER | 4,5,6 | 15/8/2012 | 15/8/2013 |
| 2 | KATE | PERRY | 4,5,6 | 15/8/2012 | 15/8/2013 |

SELECT * FROM
( (SELECT a.id ,a.name,a.surname,a.program,a.date,a.expires
from tableA a left outer join tableB b
on b.aid=a.id
where b.card=1 and (a.id between '1' and '2'))
UNION ALL
(SELECT a.id ,b.name,b.surname,a.program,a.date,a.expires
from tableA a left outer join tableB b
on b.aid=a.id
where b.card=1 and (a.id between '1' and '2'))) t
ORDER BY id
EDITED:
Please refer to http://sqlfiddle.com/#!2/d8227/1

Are you looking for -
(SELECT a.id, name, surname, program, date, expires FROM tableA a WHERE a.id BETWEEN '%id1' and '%id2')
UNION
(SELECT a.id, b.name, b.surname, program, date, expires FROM tableB b LEFT JOIN tableA a ON b.aid=a.id WHERE b.card=1 AND (a.id between '%id1' and '%id2') )
ORDER BY a.id ASC

(select a.ID,a.NAME,a.SURNAME,a.PROGRAM,a.DATE,a.EXPIRES from tableA a where ...)
Union All
(select a2.ID,b.NAME,b.SURNAME,a2.PROGRAM,a2.DATE,a2.EXPIRES from tableB b
left join tableA a2 on b.aid = a2.id where ...);
You can choose left/inner join as per your need and where condition too with between clause like.. where id between 2 and 8 or where id > 2 and id < 8.