I am trying to join two tables together using UNION (although im not sure that is the best option) there are technically two related columns however they don't have the same name so i'm assuming that isn't an option here is my query:
SELECT title, type, release_date FROM pictures
UNION
SELECT name, residence, NULL as Col3 FROM actor
ORDER BY release_date ASC;
It is only printing out the pictures columns from this? Thank you for any help in advance.
To relate two tables you could use some foreign key or a third table in the case of beign a many-to-many relation, you should use one of the join options, for example:
Imagine that exists a table that relate actor and pictures, called actor_pictures.
Image that we will relate the tables by id (it could be another one, and it doesn't have to have the same name).
You could do this:
SELECT * FROM actor_pictures ap
JOIN actor a ON ap.actor_id = a.id
JOIN pictures p ON ap.pictures_id = p.id
ORDER BY p.release_date ASC
Read this: https://www.w3schools.com/sql/sql_join.asp
Related
Hi guys I'm new with databases and I'm trying to make a query where I join 3 tables. I could make it and I want to clean up the result. I want to know how can I delete the column "pin" from users table and maybe some "ids" columns.
Select * from "wish-list"
Join products
On "wish-list".id = products.holiday_id
Join users
On "wish-list".user_id = users.id
Where "wish-list".id = 1
You need to specify which columns you really need in your output. At the moment you are using
SELECT * which outputs all columns of all joined tables.
Here is what it should look like:
SELECT holiday, products.description, users.pin FROM "wish-list"
JOIN products ON "wish-list".id = products.holiday_id
JOIN users ON "wish-list".user_id = users.id
WHERE "wish-list".id = 1
It's important that you reference all columns which are not your main entity (here wish-list) with tablename.column (products.description and not only description). It will work without referencing strictly but only if the column name is unique in your query.
Furthermore you can rename columns. This is useful for example if you want to get the id's of the product table and the wish-list table.
SELECT product.id AS product_id, id AS wishlist_id FROM "wish-list"
...
Hope that helps!
I have two tables of world countries Independence Day and I wanted to combine them into one table with a distinct id, but they are using different Primary keys, any suggestions will be appreciated.
Summary of request: How to combine two tables with different Primary Keys but the other fields in common and removing duplicate fields ideally Hash Match and removing duplicates
Expected Results this will include all the unique countries in both tables, please one table may have more countries and we want to make sure we take all the distinct countries from each table. Ideally, the solution will be likely to be of like Hash Match operator in SQL which implements several different logical operations that all use an in-memory hash table for finding matching data. Many thanks in advance
The image of two tables which needs combining.
You seem to want full join:
select a.*, b.* -- select the columns you want
from a full join
b
on a.country = b.country;
If you want to assign a new unique id use row_number():
select row_number() over (order by coalesce(a.country, b.country)) as new_id,
a.*, b.* -- select the columns you want
from a full join
b
on a.country = b.country;
I am wondering if anyone can help me, I have these tables:
tbl_search_history(id,fld_user_id,fld_username_fld_make_id,fld_model_id,fld_year_id,fld_category_id)
The fld_make is the name of the make:
tbl_make(id,fld_make)
The fld_model is the name of that model
tbl_model(id,fld_model)
The fld_year is the name of that year
tbl_year(id, fld_year)
The fld_category is the name of that category
tbl_category(id,fld_category)
Now I need to show a table in my page in which I need to have this fields: make, model, year, and category. I also want to know how can I have the make, model, year, and category names (instead of just the reference numbers from the tbl_search_history) in my page? Would you please give me a piece of code and a brief explanation?
Thanks in advance!
Your question is a bit unclear, but it sounds like a homework problem.
I will give you some pseudocode and references.
First off I would do some reading on JOINS.
If you are asking to get Column Names, see this SO question
I believe what you want to do is join your tables like so:
SELECT table1.desired_field, table2.desired_field2, table3.desired_field3
FROM table1
JOIN table2 ON table1.table2_id = table2.id
JOIN table3 ON table1.table3_id = table3.id
and so on.
SELECT
tbl_model.fld_make,
tbl_make.fld_model,
tbl_year.fld_year,
tbl_category.fld_category
FROM
tbl_search_history
INNER JOIN tbl_make ON tbl_search_history.fld_make_id = tbl_make.id
INNER JOIN tbl_model ON tbl_search_history.fld_model_id = tbl_model.id
INNER JOIN tbl_year ON tbl_search_history.fld_year_id = tbl_year.id
INNER JOIN tbl_category ON tbl_search_history.fld_category_id = tbl_category.id
Assuming that the search history table is the table that links all these other tables together. Also assuming that all of these tables have linked values (ie non-null id's in tbl_search_history) otherwise you'd need to use an OUTER JOIN.
What you want to do is to join with the make, model, year, and category tables using the ids you have in the tbl_search_history.
Something of this sort will give you want you want :
SELECT * FROM `tbl_search_history`
INNER JOIN `tbl_make`
ON tbl_search_history.fld_make_id = tbl_make.id
#keep going for model, year, and category tables using their respective ids.
Hope this helps!
I know the title is confusing but its the best I could explain it. Basically im developing a cinema listings website for a company which owns two cinemas. So I have a database which has the two tables "Films" and "Listings" with data for both cinemas in them.
I'm trying to select all films and their data for one cinema if the films name shows up in the listings (since the two cinemas share all films but in the table but the may not have the same films showing)
Here is what i have come up with but I run into a problem as when the "SELECT DISTINCT" returns more than one result it obviously cant be matched with the FilmName on tbl Films.
How can i check this value for all FilmNames on tblFilms?
SELECT *
FROM tblFilms
WHERE FilmName = (SELECT DISTINCT FilmName FROM tblListings WHERE Cimema = 1)
use IN if the subquery return multiple values,
SELECT *
FROM tblFILMS
WHERE FilmName IN (SELECT DISTINCT FilmName FROM tblListings WHERE Cimema = 1)
Another way to solve thius is by using JOIN (which I recommend)
SELECT DISTINCT a.*
FROM tblFILMS a
INNER JOIN tblListings b
ON a.FilmName = b.FilmName AND
b.Cimema = 1
for faster query execution, add an INDEX on FilmName on both tables.
If you have your schemas for the tables, that would help.
That said, I believe what you want to look at is the JOIN keyword. (inner/outer/left/etc). That's exactly what JOIN is meant to do (ie your title).
my table contains category_name and parent_category_Id column
My parent_category data contains, the same table primary key id.
i need to select the all rows and insted my parent_category_Id i need to select the catogry_name
I think this is what you're after, though it's hard to discern from the question:
Select c.*
From category c
Join parent_category pc ON c.parent_category_id = pc.id
Where pc.category_name = 'Some Name'
Try something like:
SELECT c.category_name, p.category_name
FROM categories c LEFT JOIN parent_categories p
ON c.parent_id = p.id
PS: you may think about restructuring your database, it would make more sense to store all the categories in the same table. See for instance: http://mikehillyer.com/articles/managing-hierarchical-data-in-mysql/
You should restructure your database to have one table with:
id, name, and parent columns, with the parent column referencing the same table's id column. Your current database is not normalized and will likely cause issues in the future.
At a minimum you should have an auto_increment id column in the categories table.
The other answers here are correct (depending on the SQL server you are using).