I have to get data from two SQL tables but I am unsure of what join to use and the same tables have the same customers_id table would I use an inner join?
table - customers
customers_id
customers_firstname
customers_lastname
customers_email_address
table - orders
customers_id
customers_street_address
customers_suburb
customers_city
customers_postcode
customers_state
customers_country
It depends on what results you want. If you want every record in Customers regardless of whether there is a matching record in orders the you would use an LEFT OUTER JOIN. If not you would use an INNER JOIN. This is the article I typically refer people to for a basic explanation of joins.
An INNER JOIN would look like this:
SELECT c.customers_id,
c.customers_firstname,
c.customers_lastname,
o.customers_street_address,
o.customers_city,
o.customers_postcode,
o.customers_state
FROM customers as c
INNER JOIN orders as o
ON c.customers_id = o.customers_id
I purposely did not do select *. Try to get into the habit of only selecting the columns you want from tables instead of everything.
The join you should use depends on which information you are trying to retain, based on the customer ID. If you're looking to retain all of the information from customers even if there is no match with orders you would use a left join. Conversely, if you wanted to retain all the information from orders even if there were no match with customers you would use a right join.
If you want to return all of the information, and combine rows which have a match, use a full join. Finally, you can use an inner join if you only want the rows which have a match from either table.
the same tables have the same customers_id table
I think you meant to say they have a common column, being customers_id, in which case you can use NATURAL JOIN.
INNER JOIN Ya you can use it.
You can write below query to get your all data from two tables.I am going to write full join query for you.y
select customers.customers_firstname,
customers.customer_lastname,
orders.customers_city
from customers
INNER JOIN orders
ON customer.customers_id = orders.customers_id
Related
I just recently learned about SQL INNER JOIN and I thought of applying it on a project so basically I have three tables
payers
discounts
items
Now I was just wondering if I can return the results from both of the three tables at once using an INNER JOIN with both of the 3 tables or is it only possible with 2 tables?
If it is possible to use an INNER JOIN with more than 2 tables then kindly please guide me on how to do it and if not then tell me how to do it in any other ways possible.
Now this is the query that I currently have which doesn't work as expected:
SELECT *
FROM payers
INNER JOIN discounts AND items
ON payers.id = discounts.id AND ON payers.id = items.id;
You want two joins. The syntax is:
SELECT *
FROM payers p
INNER JOIN discounts d ON d.id = p.id
INNER JOIN items i ON i.id = p.id
Side notes:
you did not show your actual schema, so this uses the join conditions described in your attempt; you might need to review that
table aliases make the query shorter to write and easier to read
SELECT * is generally not good practice; instead, I would recommend enumerating the columns you want in the SELECT clause, and properly aliasing conflicting columns names, if any (here, all three tables have a column called id, which would cause ambiguity in the resultset)
I have two mySQL statements. First is:
SELECT o.OrderID, c.CustomerName, o.OrderDate
FROM Customers AS c, Orders AS o
WHERE c.CustomerID=o.CustomerID;
The second is:
SELECT Orders.OrderID, Customers.CustomerName, Orders.OrderDate
FROM Orders
INNER JOIN Customers
ON Orders.CustomerID=Customers.CustomerID;
Both produce the same result, but second doesn't contain reference on Customers table in FROM request.
My question is - what is the difference between these two sql statements? In which cases should I use JOIN and in which cases should I use simple SELECT from two tables?
They are the same except the second is easier to read, so you should use that one.
Those JOIN are different, although the result are the same.
The First one is CROSS JOIN and adds the condition in where, which is implicit CROSS JOIN
The second one is INNER JOIN
If you want to connect two tables I would use INNER JOIN instead of CROSS JOIN Because the intention of the inner join table is clearer
I have two tables:- PERSON and DATA. What I want to do is fetch all details from PERSON table and only two columns from DATA table only when PERSON.personId = DATA.personId.
I am using this query:-
SELECT *
FROM PERSON AND SELECT DATA.value, DATA.field
FROM DATA where PERSON.personId = DATA.personId;
But I think this is wrong syntax. Can anyone tell me what is the right syntax for it.
SELECT p.*,d.column1,d.column2
FROM Person p
JOIN Data d
ON p.personId = d.personId
WHERE <Condition>
In this query person with all columns and data with your desire column you can fetch by this query.
Something like this:
select
P.*,
D.value,
D.field
from Person P
join Data D on P.PersonID = D.PersonID
change P.* to the specific columns that you need but P.* will get everything from the Person table.
check this post out LEFT JOIN vs. LEFT OUTER JOIN in SQL Server to learn about JOINS, the diagram is good to understand what the different ones do
Its really easy, Just execute this query:
SELECT
PERSON.*,
DATA.value,
DATA.field
FROM
PERSON INNER JOIN DATA USING (`personId`);
It selects all fields of PERSON + value and field from DATA.
Also it uses personId to join the two tables.
Fill free to ask if you need more info.
You can use join (LEFT JOIN)
SELECT * FROM PERSON LEFT JOIN DATA ON PERSON.personId = DATA.personId
Hope it will help you
Here's the correct syntax for achieving what you've asked for:
SELECT PERSON.column1,PERSON.column2,PERSON.columnN,DATA.value
FROM PERSON
INNER JOIN DATA
ON PERSON.personId = DATA.personId
Line#1: lists the columns that you want to select with references to their parent tables.
Line#2 and 3: are the two tables that you want to select from and join with
Line#4: is the join condition between the two tables (with matching IDs or other information)
It's been so long since I did any Mysql queries I forgot how to do basic joins. I have two tables:
Orders_ and
Members
I need to create one view which displays all the orders with the associated Email and Member_Id.
http://i.imgur.com/7ttXtrk.png <-- Tables
The query, based on your image, should look like so:
SELECT Orders.*, Members.*
FROM Orders
INNER JOIN Members ON Orders.coordinateList_Id = Members.Members_Member`
I would refer to the MySQL reference
SELECT *
FROM Orders
INNER JOIN Members
ON Orders.coordinateList_Id = Members.Members_Member
I have a table in my DB called ORDERS and it looks like this:
ID_section (int), ID_price (int), ID_city (int), ID_company (int)
And I want to use the JOIN method to set names to the ID's.
What I would do is:
SELECT * FROM ORDERS
JOIN sections ON sections.id=orders.ID_section
JOIN prices ON prices.id=orders.ID_price
JOIN cities on cities.id=orders.ID_cities
JOIN companies ON companies.id=orders.ID_company
But the point is, that in ORDERS table can be inserted value of 0 and it means - all the sections/prices/cities/companies, but when I run my query, only the values, that their ID exist in the other table show up.
Any ideas? Thanks.
If I understand you question correctly and having, for example, ID_section = 0 means that the order belongs to all the section then the following query should do the trick.
SELECT * FROM ORDERS
JOIN sections ON sections.id=orders.ID_section OR orders.ID_section = 0
JOIN prices ON prices.id=orders.ID_price OR orders.ID_price = 0
JOIN cities on cities.id=orders.ID_cities OR orders.ID_cities = 0
JOIN companies ON companies.id=orders.ID_company OR orders.ID_company = 0
If, on the other hand, you want to retrieve all orders regardless if they have sections, prices, etc. associated, then it is sufficient to put LEFT JOIN where you have JOIN. (But this situation does not result from your question! I only added it because people seem to understand that.)
Use LEFT JOIN instead of JOIN (which is a shorthand for INNER JOIN)
Experiment with LEFT and RIGHT OUTER JOIN s and you'll be able to figure out what you need to do. Basically a LEFT or RIGHT OUTER JOIN will insert NULLS into columns where no data exists but still do the joins.
There are various resources on the web that explain this.