I have two tables
table A contain many ids, which one is related to the table B.
I have to make a query on the table A to select only some ids and then take the data from the table B using the selected ids from the table A
How can i do that? (MYSQL)
Based on your description, here is a simple structure of how the query might go, although I recommend you share some sample results & the desired output.
SELECT * FROM tableA
JOIN tableB
ON tableA.id_song == tableB.id_song
WHERE "your condition HERE"
Related
I am having a table "all_data" which consists 2 set of records
a) Independent records which should get fetched all times
b) All records from table "all_product"
Now I am also having few more tables like
'MS_product', 'apple_product' ,'Linux_product' and all these tables are subset of table 'all_product'.
I already have used left or right join but looks like this will not be usefful.
I want to fetch all the Independent records from table 'all_data' and only matched records from other tables i.e. 'ms_product' so final output should have
all independent records + matched record from 'MS_product' or 'apple_product' or 'Linux_product' table.
You can use the MINUS operator for the first query :
SELECT *
FROM all_records
MINUS
(
SELECT *
FROM MS_product
UNION
SELECT *
FROM Apple_product
)
It will gives you all the tuples who are not in the MS_product and Apple_product tables.
However I don't recommend to design your database like you are doing. Prefer a single table with a dedicated column for the brand product.
brand new to complex mysql queries. I have a database schema that includes a pair of tables that I need to combine:
In the first table avatars, I have columns user_id, url, and name, with a single row for each unique user_id. In the second table interpretations I have user_id and scan_index plus 3 other fields. I'd like to generate a mysql result that matches a specific scan_index from interpretations, includes all columns from this table and additional corresponding fields url, and name from avatars. Should I be using JOIN or UNION to do this query?
JOIN is used to combine both tables on the basis of column values (here in your case, i guess, its user_id), your query can be something like this :
SELECT url, name, scan_index,...
FROM avatars
LEFT JOIN interpretations
ON avatars.user_id = interpretations.user_id
WHERE interpretations.scan_index = *your_specific_value*
You need to use join. To explain it very simply, a join combines 2 tables by placing the data from the 2 tables next to each other, while a union combines 2 queries by placing the data below each other.
I have two tables that have different data that I need to merge. They do have similarities such as: Order number, Name, type or product. But they have separate data as well like: Order date, and Engravings.
Would I do two separate Append queries in Access into a merged table? Or one Append queries? Or just keep the data separate?
I am new to Access and trying to find the best way to approach this.
Merging the two tables into one completely defeats the purpose of using a database and you're better off using excel at that point. You want to split the data as much as possible along logical lines so that you can find, say... all the orders that Mr X has ever made for a specific product. And in that case you're going to want to have separate tables for customers, orders, engravings and the like.
The best practice from a design standpoint is to place fields that each table has in common into a third "master" table, then create relationships from that table to the existing tables and delete the data that has been transferred to the main table (except for the primary keys, which have to be common with your master table).
To create the master table, use a Make Table query to generate the master table based on one of your tables, then an append query to add any products in the master table that might not be common to both, based on the other table. Finally, delete queries for each table would rid you of redundant data in both original tables.
However, I strongly suggest you use Microsoft's tutorials and download the NorthWind sample database so you can get an idea of what a properly structured database looks like. The beginner's learning curve for access is very steep and having well built example databases is almost a requisite.
Make a backup of your database(s) and play with it until it turns out right. Do not make the mistake of playing with live data until you know what you're doing.
As you have similar fields on either table, take the Order number field from both tables using a union query. Something like:
SELECT tbl_Delivery_Details.OrderNo
FROM tbl_Delivery_Details
GROUP BY tbl_Delivery_Details.OrderNo
UNION
SELECT tbl_Delivery_Header.[Order number]
FROM tbl_Delivery_Header
GROUP BY tbl_Delivery_Header.[Order number];
This would take the order numbers from the delivery details table and from the delivery header table and merge them into one list with only one instance of each order number. Save the query.
You could then use this query in a new query. Bring in your 2 tables to this query and insert the fields from either table that you require.
As users add records to the tables they will be added to the union selet query when it is next run.
PB
It depends on what you want to do. Let's assume you have tables A (with 50 records) and B (with 75) records, and both tables have a similar column called OrderID.
Appending Rows:
If you want to create a table with 125 total records by combining records (rows) from A and records (rows) from B, run the following two queries:
Query 1:
SELECT A.ORDER_NUMBER, A.TEXT_FIELD1 as DATA INTO C
FROM A;
Query 2:
INSERT INTO C ( ORDER_NUMBER, DATA )
SELECT B.ORDER_NUMBER, B.TEXT_FIELD2
FROM B;
Appending Columns: If you want to create a table with 75 total records where you are appending columns from A to the columns in B, then run the following query:
SELECT B.ORDER_NUMBER, A.TEXT_FIELD1, B.TEXT_FIELD2 INTO C
FROM A RIGHT JOIN B ON A.ORDER_NUMBER = B.ORDER_NUMBER;
... in a similar way, you can append columns in B to columns in A in a new table C with a total of 50 records by running the following query:
SELECT A.ORDER_NUMBER, A.TEXT_FIELD1, B.TEXT_FIELD2 INTO C
FROM A LEFT JOIN B ON A.ORDER_NUMBER = B.ORDER_NUMBER;
I am trying to create a table that shows treatment information about patients (though I just wondered if would be better as a query) at a fictional hospital. The idea is that one row of this could be used to print an information sheet for the attending nurse(s).
I would like to make the attending_doctor column contain the name that corresponds with the employee_id.
|Patient_ID|Employee_ID|Attending_Doctor|Condition|Treatment|future_surgery|
Would appreciate any help. Thank you!
Just use a join in your query rather than have the employee name in 2 tables (which would mean updating in more than one location if they change name etc). For the sake of an example, this also gets the patients name from a 3rd table named patients.
eg
SELECT table1.*, employees.name, patients.name
FROM table1
LEFT JOIN employees ON employees.id = table1.employeeId
LEFT JOIN patients ON patients.id = table1.patientsId
Don't use directly this table, but build a view that contains the data you need. Then you can get the data from the view like it was a table.
Basically what you need is to have data in three tables. One table for patients, one table for for employees and one for the reports. Table with reports should contain only the employee_ID. Then you can either build a direct query over these three tables or build a view that will hide the complicated query.
I wanted to know if it was possible to make a select on a table that contains multiple field and join them in 1 result :
Example :
Table :
id
dayOne_City
dayTwo_City
dayThree_City
Result : one column that contains the rows of all the cities (Distinct).
2) Am i better to do a view if i have a lot of query to that specific list ?
3) should i do 3 select with union ?
Thank you
You should be fine with:
select dayOne_City from YourTable
UNION
select dayTwo_City from YourTable
UNION
select dayThree_City from YourTable
However, you should review your design to allow multiple cities per whatever-is-that-your-table stores. That is, create an actual many-to-many relationship by creating an intermediate table between YourTable and Cities.
select concat_ws(',', id, dayOne_city, dayTwo_city, dayThree_city, etc...) as allInOne
Details on the function used here. However, I should ask why you're doing this. By joining the fields together, you're destroy any chance of reliably extracting/separating the data again later. Only do this kind of "bulking" if you never plan on using separate portions of the data elsewhere based on the results of this query.