I need to get contact information where employee id is null and not null. How do I join the same table with these different conditions. I need the information to populate a report with both employee information and person accompanied them to a event. Here is the query I have so far.
select events.id, (persons.firstname+' '+ persons.lastname) as employee
from events
inner join eventscontacts on events.id = eventcontacts.events_id
inner join contacts on eventcontacts.contact_id = contacts.id
inner join persons on contacts.person_id = person.id
Eventcontacts table
Id ContactType_id contact_id event_id
1 1 1 300
2 2 3 300
Contact type is 1 for employee and 2 for non emplopyees
contacts table
Id person_id employee_id
1 100 200
2 101 201
3 102 NULL
4 103 202
5 104 203
Person table
Id firstname lastname
100 John Stewart
101 Greg Larry
102 Kim Hans
103 Gloria June
104 Dan Duke
Result table
ID employee accompany
300 John Stewart Kim Hans
right now, I have information of all the employees for the event. I want the people who accompanied these person for the events. Their employee id is null in the contacts table. How do I join the contacts table again here?
An inner join will return only the rows that exist in both tables, where it seems like you want all the rows from the contacts table including the rows that don't match due to them lacking an employee id.
If you use an outer join, it will return rows that exist in contacts AND in events like an inner join but ALSO rows that ONLY exist in events and rows that ONLY exist in contacts.
In the case that I am explaining this poorly, I recommend you read this to help explain:
https://mode.com/sql-tutorial/sql-outer-joins/
If you can successfully use an outer join you will get all the visitors in one table regardless of having an id or not.
Related
I have a table where I have employee data by week... Let's say I just have 3 employees. I need to track their information weekly, because we might change their supervisor in any week and employee performance will also count towards supervisor performance
week
employeeId
employeeName
supervisor
2022-07-10
1
David
Bob
2022-07-10
2
Joe
Bob
2022-07-10
3
Miriam
Martin
2022-07-17
1
David
Bob
2022-07-17
2
Joe
Bob
2022-07-17
3
Miriam
Martin
I have another table, where I track sales, I just have the employeeId showing to that table.
week
employeeId
sales
2022-07-10
1
$500
2022-07-10
2
$400
2022-07-10
3
$309
I want to create a new table that show how's their supervisor with left join
FROM company.sales AS t
LEFT JOIN company.employee_roster AS roster
ON
roster.week = t.week
AND roster.employeeId = t.employeeId
But I always get duplicated data... If I remove the JOIN statement, I get the data as intended without the supervisor's name.
Is the above approach the right one? Is there any better way to join those tables?
Use below
SELECT *
FROM `company.sales` AS t
LEFT JOIN `company.employee_roster` AS roster
USING(week, employeeId)
with output
or just use below (this cover scenario when columns to be joined can have different names)
SELECT t.*, employeeName, supervisor
FROM `company.sales` AS t
LEFT JOIN `company.employee_roster` AS roster
ON t.week = roster.week
AND t.employeeId = roster.employeeId
This is my very first Stackoverflow post, so I apologize if I am not formatting my question correctly. I'm pounding my head against the wall with what I'm sure is a simple problem. I have a table with a bunch of event information, about 10 columns as so:
Table: event_info
date location_id lead_user_id colead_user_id attendees start end <and a few more...>
------------------------------------------------------------------------------------------------
2020-10-10 1 3 1 26 2100 2200 .
2020-10-11 3 2 4 18 0600 0700
2020-10-12 2 5 6 6 0800 0900
And another table with user information:
Table: users
user_id user_name display_name email phone city
----------------------------------------------------------------------
1 Joe S goofball ...
2 John T schmoofball ...
3 Jack U aloofball ...
4 Jim V poofball ...
5 Joy W tootball ...
6 George A boring ...
I want to create a view that has only a subset of the information, not full table joins. The event table lead_user_id and colead_user_id columns both refer to the user_id column in the users table.
I want to create a view like this:
date Location Lead Name CoLead Name attendees
---------------------------------------------------------------------
2020-10-10 1 Jack U Joe S 26
2020-10-11 3 John T Jim V 18
2020-10-12 2 Joy W George A 6
I have tried the following and several iterations like it to no avail...
SELECT
E.date, E.location,
U1.display_name AS Lead Name,
U2.display_name AS CoLead Name.
E.attendees
FROM
users U1, event_info E
INNER JOIN
event_info E ON U1.user_id = E.lead_user_id
INNER JOIN
users U2 ON U2.user_id = E.colead_user_id
And I get the dreaded
You have an error in your SQL Syntax
message. I'm not surprised, as I've really only ever used joins on single columns or nested select statements... this two columns pointing to one is throwing me for a loop. Help!
correct query for this matter
SELECT
E.date, E.location,
U1.display_name AS Lead Name,
(select display_name from users where user_id=E.colead_user_id) AS CoLead Name,
E.attendees
FROM
event_info E
INNER JOIN
users U1 ON U1.user_id = E.lead_user_id
I want to join fields from different tables into one doing a query with joins. From now I've only joined two tables but I have difficulties merging others more. Can you help me? These are my tables:
Table Departments
------------------------------------
Department_ID Department_Name
------------------------------------
1 Sales
2 Marketing
3 Warehouse
Table Roles
---------------------------------
Role_ID
---------------------------------
1
2
3
4
Table Departments_Roles
--------------------------------------------------------------------
Dep_Role_ID Department_ID Role_ID Role_Name
--------------------------------------------------------------------
1 1 1 Admin
2 1 2 Client Attention
3 2 1 Admin
4 3 2 Client Attention
Table Employers
---------------------------------
Employer_Id Employer_Name
---------------------------------
1 John
2 Jess
3 Tom
4 George
5 David
What I want to see is:
Table Merged
-------------------------------------------------
Department_Name Employer_Name Role_Name
-------------------------------------------------
xxxxx yyyyy zzzz
This are just some example tables. Dont look for the sense of it.
I've tried using join, but I've never make something so complex.
Can you give me some advice?
Joining multiple tables is the same as joining one table, just repeated.
SELECT D.Department_Name, E.Employer_Name, DR.Role_Name
FROM Employers E --this is your base table
INNER JOIN magicalEmployerToDepartmentRoleLinkTable EDR --this connects our base table to the linking table
ON E.Employer_Id = EDR.Employer_Id
INNER JOIN Department_Roles DR --now we can pull any column in the Department_Roles table that is related back to our base table
ON ED.Department_Id = DR.Department_Id
INNER JOIN Department D --now we can pull any column in the Department table that is related back to the Department_Roles table
ON DR.Department_ID = D.Department_Id
I have a requirement in such a way that it should join two tables with more than 100k records in one table and just 5 records in another table as shown below
Employee Dept Result
id Name deptid deptid Name Name deptid Name
1 Jane 1 1 Science Jane 1 Science
2 Jack 2 2 Maths Dane 1 Science
3 Dane 1 3 Biology Jack 2 Maths
4 Drack 3 4 Social Drack 3 Biology
5 Drim 5 Zoology Kery 4 Social
6 Drum 5 Drum 5 Zoology
7 Krack
8 Kery 4
.
.
100k
Which join need to be used to get the query in an better way to perform to get the result as shown.
I just want the query to join with other table from employee table only which has dept which i thought of below query but wanted to know is there any better way to do it.
Select e.name,d.deptid,d.Name from
(Select deptid,Name from Employee where deptid IS NOT NULL) A
and dept d where A.deptid=d.deptid;
Firstly not sure why you are performing your query the way you are. Should be more like
SELECT A.name, D.deptid,D.Name
FROM Employee A
INNER JOIN dept D
ON A.deptid = D.deptid
No need of the IS NOT NULL statement.
If this is a ONE TIME or OCCASIONAL thing and performance is key (not a permanent query in your DB) you can leave out the join altogether and do it using CASE:
SELECT
A.name, A.deptid,
CASE
WHEN A.deptid = 1 THEN "Science"
WHEN A.deptid = 2 THEN "Maths"
...[etc for the other 3 departments]...
END as Name
FROM Employee A
If this is to be permanent and performance is key, simply try applying an INDEX on the foreign key deptid in the Employee table and use my first query above.
good day, i have these 3 tables...i.e.;
customer table
cust_id cust_name sales_employee
1 abc 1
2 cde 1
3 efg 2
transaction table
order_num cust_id sales_employee
1001 1 1
1002 2 2
sales_employee table
sales_employee employee name
1 john doe
2 jane doe
how can i show the employee name on both customer table and transaction table?
notice how the sales_employee can change per transaction, it does not necessarily have to be the same per customer.
please help.
To select customers with sales person name
select
C.*, E.employee_name
from
Customers as C
inner join Sales_Employees as E on E.sales_employee = C.sales_employee
To select transactions with customer name and salesperson name (at the point in time of the transaction)
select
T.*,
E.employee_name as Trans_employee,
C.cust_name,
EC.employee_name as Cust_employee
from
Transactions as T
inner join Sales_Employees as E on E.sales_employee = T.sales_employee
inner join Customers as C on C.cust_id= T.cust_id
inner join Sales_Employees as EC on EC.sales_employee = C.sales_employee
This code is meant to guide you, you will need to adjust it to match your table and field names.