These are my tables(with some records):
Product:
ID PRICE NAME DESCRIPTION
1 100 laptop laptop_desc
2 200 mouse mouse_desc
3 300 伊吾 伊吾伊吾
Product_Translations:
PID LANG NAME DESCRIPTION
1 ch 伊吾 伊吾伊吾
And using the following query I could JOIN the 2 tables:
SELECT p.id,p.price,
COALESCE(pt.Name, p.Name) Name,
COALESCE(pt.Description, p.Description) Description
FROM Product p
LEFT JOIN Product_T pt
ON pt.PID = p.ID
AND pt.LANG = 'ch'
WHERE (UPPER(p.name) LIKE UPPER('%伊吾%') OR UPPER(pt.name) LIKE UPPER('%伊吾%'))
Now my question is that in the above query I need to mention each and every column in the select query explicitly(like p.id, p.price; real table has lot more columns) which I don't want to do. In my case I need to get all columns all the time, i.e, select *. But If give p.* in the query, name and description columns are coming twice which is expected(from Product and Product_T tables). So is there any way I could still give p.* and get the merged name and description columns ?
Thanks for your help.
You could query the schema to find the columns on your tables and then dynamically build your select statement from that. (E.g. if a column with the same name appears in both tables only select it from one of them).
See http://hsqldb.org/doc/2.0/guide/databaseobjects-chapt.html#dbc_information_schema for information on how to query the schema in hsqldb.
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!
From the code as shown below. I wonder that why it can select data from 2 tables in same time that are table "venue AS v" and table "as s".
or I misunderstand?
SELECT name, s.num_match
FROM venue AS v,
(SELECT venue_id, COUNT(*) AS num_match
FROM match
GROUP BY venue_id) AS s
WHERE v.venue_id = s.venue_id
LIMIT 3;
Yes you can using JOIN clause for example.
More infos here: https://www.informit.com/articles/article.aspx?p=30875&seqNum=5
Yes you can select data from as many as tables you want at the same time.
In this case you are trying to get an aggregated number from table-s and join it with the table v.
There are many ways to write the code to join the table. Above is one method which you have used.
I have a table called Target where I have 5 columns:
ProductLevel
ProductName
CustomerLevel
CustomerName
Target
In another table called Products I have 3 columns:
ProductId
ProductCategory
ProductBrand
In the 3rd table called Customer I have 3 columns:
CustomerID
CustomerName
SubCustomerName
Is there a way to do a dynamic join where I select the column I will use in the JOIN based on the value that I have in the 1st table?
Example: If in the first table I have Category in ProductLevel, I'll join the table product using ProductCategory field. If I have Brand, I'll join using ProductBrand... The same happens with Customer table.
PS: I'm looking for a way to create it dynamically in a way I can add new columns to that tables without changing my code, then in the future I can have ProductSegment column in Product Table and Segment as a value in ProductLevel in Target table.
Yes, like this:
SELECT * FROM
Target t
INNER JOIN
Product p
ON
(t.ProductLevel = 'Category' AND t.??? = p.ProductCategory)
OR
(t.ProductLevel = 'Brand' AND t.??? = p.ProductBrand)
You didn't say which column in Target holds your product category/brand hence the ??? in the query above. Replace ??? with something sensible
PS; you can't do as you ask in your PS, and even this structure above is an indicator that your data model is broken. You can at least put the code in for it now even if there are no rows with t.ProductLevel = 'Segment'
Don't expect this to perform well or scale.. You might be able to improve performance by doing it as a set of UNION queries rather than OR, but you may run into issues where indexes aren't used, crippling performance
Hi I’m trying to write a query and I’m struggling to figure out how to go about it.
I have a suppliers table and a supplier parts table I want to write a query that lists suppliers that have specified related Parts in the supplier parts table. If a supplier doesn’t have all specified related parts then they should not be listed.
At the moment I have written a very basic query that lists the supplier if they have a related supplier part that meets the criteria.
SELECT id ,name
FROM
efacdb.dbo.suppliers INNER JOIN [efacdb].[dbo].[spmatrix] ON
id = spmsupp
WHERE spmpart
IN ('ALUM_5083', 'ALUM_6082')
I only want to show the supplier if they have both parts related. Does anyone know how I could do this?
Use a subquery with counting distinct occurences:
select * from suppliers s
where 2 = (select count(distinct spmpart) from spmatrix
where id = spmsupp and spmpart in ('ALUM_5083', 'ALUM_6082'))
As a note, you can modify your query to get what you want, just by using an aggregation:
SELECT id, name
FROM efacdb.dbo.suppliers INNER JOIN
[efacdb].[dbo].[spmatrix]
ON id = spmsupp
WHERE spmpart IN ('ALUM_5083', 'ALUM_6082')
GROUP BY id, name
HAVING MIN(spmpart) <> MAX(spmpart);
If you know there are no duplicates, then having count(*) = 2 also solves the problem.
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).