I'm trying to query my database for unused listId's but can't quite seem to get the query syntax correct. Here is what I've tried:
SELECT DISTINCT pkListId FROM tblList
INNER JOIN InUseLists ON
tblList.pkListId NOT LIKE InUseLists.fkListId
Where tblList holds all List data, and InUseLists is a view holding all distinct listId's from my relational table.
Currently my tblList holds listId 1-9
my relational table has fkListId 1,8,9 (used more than once)
So my view gets distinct values from the relational table - 1,8,9.
What is wrong with my query syntax?
It sounds like you want a left join (which can succeed whether or not it finds a match in the "right" table), and then to select those rows where the join, in fact, failed to work.
Something like:
SELECT DISTINCT pkListId FROM tblList
LEFT JOIN InUseLists ON
tblList.pkListId LIKE InUseLists.fkListId
WHERE InUseLists.fkListId is null
(If LIKE is the right operator here. Most joins use a simple equality check)
If this still isn't right, it might be better if you edited your question to include the sample data and expected results in a tabular form. At the moment, I'm still not sure what the contents of your tables are, and what you're aiming for.
Try:
SELECT DISTINCT tblList.pkListId, FROM tblList, InUseLists WHERE
tblList.pkListId NOT IN(InUseLists.fkListId)
Related
Could someone please tell explain to me how to properly process a query that collects information from 2 tables, i thought I had this figured out until I added more records. Please look at the image I have below:enter image description here
(The last record should not have the name "Thomas Murray" in it)
Then there is the query I am processing:
"select a.*, b.forenames, b.surname FROM playerSkills a, playerdb b GROUP BY sheetNo"
What I was hoping to do is collect all from the playerSkills database (which it does) and only bring over the names from the second database (playerdb) that matched with the playerID but as I want to return more than one result so I don't know what to do as it returns the whole column and just pastes the one name into every field.
Though I am sure a JOIN is to be inserted here, I am not sure which or at all.
I am not experienced with SQL but trying to wrap my head around it. I have experimented with the JOIN clauses but didn't get far probably due to a syntax.
How can join the names to the playerID so they appear in the appropriate fields?
You need columns to join on . . . and proper join syntax:
select ps.*, p.forenames, p.surname
FROM playerSkills ps JOIN
playerdb p
ON ps.playerId = p.playerId;
Notes:
Your query does not require GROUP BY.
Your query does require JOIN conditions.
Kudos for using table aliases. They should be abbreviations for the table name.
You want to always use explicit JOIN syntax. No commas in the FROM clause.
I have these two tables:
Achievement:
Achieves:
Question:
I want to retrieve rows from table Achievement. But, I do not want all the rows, I want the rows that a specific Steam ID has acquired. Let's take STEAM_0:0:46481449 for example, I want to check first the list of IDs that STEAM_0:0:46481449 has acquired (4th column in Achieves table states whether achievement is acquired or not) and then read only those achievements.
I hope that made sense, if not let me know so I can explain a little better.
I know how to do this with two MySQL statements, but can this be done with a single MySQL statement? That would be awesome if so please tell me :D
EDIT: I will add the two queries below
SELECT * FROM Achieves WHERE Achieves.SteamID = 'STEAM_0:0:46481449' AND Achieves.Acquired = 1;
Then after that I do the following query
SELECT * FROM Achievement;
And then through PHP I would check the IDs that I should take and output those. That's why I wanted to get the same result in 1 query since it's more readable and easier.
In sql left join, applying conditions on second table will filter the result when join conditions doesn't matter:
Select * from achievement
left join achieves on (achievement.id=achieves.id)
where achieves.acquired=1 and achieves.SteamID = 'STEAM_0:0:46481449'
Besides,I suggest not using ID in the achieves table as the shared key between two tables. Name it something else.
I don't think a left join makes sense here. There is no case where you don't want to see the Achievement table.
Something like this
SELECT *
FROM Achieves A
JOIN Achievement B on A.ID = B.ID
WHERE A.SteamID = 'STEAM_0:0:46481449'
AND A.Acquired = 1;
I have this 2 two views. I made a view out of them because they have dependencies on other tables. I then created a query joining them together. Two queries separately has over 30k plus data.
Sample Query would be like:
Select main.*, detail.*
FROM main_data as main
INNER JOIN detail_data AS details ON (main.id = detail.main_id)
WHERE main.column_data LIKE '%something%'
This is slow but if I comment out the "detail.*" on the column section with the join being there is returns the data very fast. What is wrong here?
The expected amount of data is only 20 rows. Still takes very long to perform the select. What makes it slow?
I'd like to add that the joined tables on the view are correct. It is joined accordingly. Like I said If queried separately it returns a lot of data in a very short time.
For more details, actually there is a third table here where both table are a child to. I changed it up to something like this. It improves the performance a bit.
Select main.*, detail.*
FROM parent_data AS par
INNER JOIN main_data as main ON (par.id = detail.par_id)
INNER JOIN detail_data AS details ON (par.id = detail.par_id)
WHERE main.column_data LIKE '%something%'
I made a EXPLAIN SELECT on the exact tables and this is there result:
Thank you.
The only reason the query slows down if you include fields in the resultset from detail table is that detail.main_id is indexed, therefore if no fields are selected from detail, then mysql does not have to touch detail table, it is enough to use the index only. If you do include some fields from that table, then simple index lookup will not be enough, mysql will have to open detail table and get the corresponding records from there.
Try using left join cause you need only connected records from right table:
Select main.*, detail.*
FROM main_data as main
LEFT JOIN detail_data AS details
ON (main.id = detail.main_id AND main.column_data LIKE '%something%')
I have three tables 'users', 'friends', 'friendsrequests'.
'Users' contains an id, a firstname and a lastname, 'friends' and 'friendsrequests' both contain users_id_a and users_id_b.
When I search for new friends, I select id's where firstname is LIKE :whatever or lastname LIKE :whatever. However, I want to exclude those id's which are present in the other two tables.
I know how to solve this via application logic, but I also know I shouldn't do this. I know I shouldn't chain the SELECT statements and that I should use joins.
You've answered your own question in that you know you can use joins. There are plenty of examples available here on how to do a join in MySQL.
There are several join types but the one you require in this instance is probably a LEFT OUTER. You could do a then do the filtering on the field on the other two tables by using a IS NULL. So what this is doing is joining on the additional tables regardless if there is any data in those tables. Using a WHERE IS NULL to filter out those that are present.
Rather than using joins you could take a WHERE NOT EXISTS approach. This logic might be more up your street if you're not familiar with SQL joins.
An example might be:
SELECT * FROM FRIENDS f
WHERE NOT EXISTS (SELECT 1 FROM friendsrequests fr WHERE f.user_id = fr.user_id)
Some examples can be found here:
SELECT * WHERE NOT EXISTS
Another approach in using the IN statement or specifically the WHERE NOT IN (SELECT ...)
Hopefully this will guide you if you're still stuck post your exact sql schema and the requirement on a site like http://sqlfiddle.com/ and you'll more likely get more specific response.
I have a table called faq. This table consists from fields faq_id,faq_subject.
I have another table called article which consists of article_id,ticket_id,a_body and which stores articles in a specific ticket. Naturally there is also a table "ticket" with fields ticket_id,ticket_number.
I want to retrieve a result table in format:
ticket_number,faq_id,faq_subject.
In order to do this I need to search for faq_id in the article.a_body field using %LIKE% statement.
My question is, how can I do this dynamically such that I return with SQL one result table, which is in format ticket_number,faq_id,faq_subject.
I tried multiple configurations of UNION ALL, LEFT JOIN, LEFT OUTER JOIN statements, but they all return either too many rows, or have different problems.
Is this even possible with MySQL, and is it possible to write an SQL statement which includes #variables and can take care of this?
First off, that kind of a design is problematic. You have certain data embedded within another column, which is going to cause logic as well as performance problems (since you can't index the a_body in such a way that it will help the JOIN). If this is a one-time thing then that's one issue, but otherwise you're going to have problems with this design.
Second, consider this example: You're searching for faq_id #123. You have an article that includes faq_id 4123. You're going to end up with a false match there. You can embed the faq_id values in the text with some sort of mark-up (for example, [faq_id:123]), but at that point you might as well be saving them off in another table as well.
The following query should work (I think that MySQL supports CAST, if not then you might need to adjust that).
SELECT
T.ticket_number,
F.faq_id,
F.faq_subject
FROM
Articles A
INNER JOIN FAQs F ON
A.a_body LIKE CONCAT('%', F.faq_id, '%')
INNER JOIN Tickets T ON
T.ticket_id = A.ticket_id
EDIT: Corrected to use CONCAT
SELECT DISTINCT t.ticket_number, f.faq_id, f.faq_subject
FROM faq.f
INNER JOIN article a ON (a.a_body RLIKE CONCAT('faq_id: ',faq_id))
INNER JOIN ticket t ON (t.ticket_id = a.ticket_id)
WHERE somecriteria