in my local website, people can pass a test, and administrator can see the result.
before, all the result were display but it was ugly, so I decided to show only the last test people pass. but I'm stuck because I can show only one result per person, but I can't sort him by date :(
SELECT * FROM resultateval join personne using (id) group by id
this is the query who show one result per people and here is the table.
it's supposed to show
654321 / 08-06-2018 / 12 : 02 / 5 / 8 / 1
A256589 / 05-06-2018 /13 : 05 / 7 / 10 / 2
Thank you!
Because you stored time and date separately, the query you'll need to do this is relatively ugly. We can form an effective timestamp by using ADDTIME to add the heuereeval time to the dateeval date. Then, this is just a basic aggregation join query:
SELECT t1.*
FROM resultateval t1
INNER JOIN
(
SELECT id, MAX(ADDTIME(dateeval, heureeval)) AS max_date
FROM resultateval
GROUP BY id
) t2
ON t1.id = t2.id AND
ADDTIME(t1.dateeval, t1.heureeval) = t2.max_date;
Demo
For future reference, avoid storing the date and time separately, unless there is a very good reason for doing so (and I don't see one here).
Edit: As a I feared, based on comments it appears that you have stored your dates as text. You can use the following function call to generate a date based on the date's text:
STR_TO_DATE(dateeval, '%d-%m-%Y')
Just replace in my original query dateeval with the above call to STR_TO_DATE and it should still work.
What you are doing is very wrong. You group by id, but you select all columns. As id is not unique in your joined data, this makes no sense and is invalid SQL. You cannot say: "Give me the dateeval (etc.) for the id". You must say something like: " "Give me the minimum / maximum / average dateeval for the id".
This query should result in an error, but MySQL outside ONLY_FULL_GROUP_BY mode let's this slip and silently converts select * to select id, any_value(dateeval), any_value(heureeval) .... So you get arbitrarily picked values that can even stem from different records.
What you want is something like this:
select *
from resultateval
join personne using (id)
where (id, timestamp(dateeval,heureeval)) in
(
select id, max(timestamp(dateeval,heureeval))
from resultateval
join personne using (id)
group by id
);
Related
I have two tables tableOne = 90K data and tableTwo = 100k data, i will look for the duplicate numbers on both tables with the given conditions and the matching must be 1:1 if multiple match are on the other table only one will be tagged as match (given that the data on both tables has match data).
I have this select statement below, but when i run it on my local xampp and even on CMD the screen freezes after i press enter then it takes hours before it returns an error out of memory. Hope you can help me with this.
SELECT rNum,
cDate,
cTime,
aNumber,
bNumber,
duration,
tag,
aNumber2,
bNumber2,
'hasMatch',
concatDate,
timeMinutes
FROM tableOne a
LEFT JOIN
tableTwo b ON a.aNumber2 = b.aNumber2
AND a.bNumber2 = b.bNumber2
WHERE a.hasMatch = 'valid'
AND (a.duration - b.duration) <= 3
AND (a.duration - b.duration) >= -3
AND TIMEDIFF(a.concatDate,b.concatDate) <= 3
AND TIMEDIFF(a.concatDate,b.concatDate) >= -3
Thank you In advance.
If you're doing 1:1 relationship with two tables then I think you should probably go with INNER JOIN rather than LEFT JOIN
Secondly, your query doesn't seem to be indexed properly. So, better would be using EXPLAIN SELECT ... to see the profile of SQL and create INDEXES for Filters.
in your SELECT you have aNumber2 and based on your join rule both table a and table b have aNumber2 column. it's a problem. if two table have a column with the same name, on select you should specify the table.
for example like this
SELECT a.aNumber2 as a_number2,....
in your query the same problem exists for other columns like duration and concatDate
another thing is you should use INNER JOIN in your case instead of LEFT JOIN.
if you final result have many rows(thousands), take them step by step... add LIMIT to your example and take 100 result each time.
I'm having some problems retrieving data from two tables and then listing them. I'd like to list the user's feed posts and their likes activity all in one.
Feeds - Table for users posts
Likes - Table for users likes (So when a use likes a post, a record is added to likes (Table likes contains data which contains the feeds ID of the post liked)
What I'm attempting to make: List BOTH feeds and user's Like activity in an ACTIVITY WALL.
So it should output like (ordered by timestamp desc):
"THIS IS A POST by user A"
Shows that user C liked user B's post
"THIS IS A POST by user B"
"THIS IS A POST by user L"
Shows that user A liked user F's post
"THIS IS A POST by user F"
-and it goes on-
My current SQL:
SELECT * FROM feeds,likes WHERE feeds.deleted!=0 or likes.deleted!=0 ORDER BY feeds.timestamp, likes.timestamp
However, my problem is I have no idea how to link both tables, since the IDs in my 'feeds' differ from those in 'likes'
To combine the two sets, you can use a UNION ALL set operator.
Something like this:
SELECT f.timestamp AS `timestamp`
, 'feed' AS `src`
, f.feed_id AS `id`
, f.feed_content AS `content`
FROM feeds f
WHERE f.deleted!=0
UNION ALL
SELECT l.timestamp AS `timestamp`
, 'like' AS `src`
, l.like_id AS `id`
, l.note AS `content`
FROM likes l
WHERE l.deleted!=0
ORDER BY 1 DESC
Note the the queries (on either side of the UNION ALL operator) need to match, in terms of the number of columns returned, and the datatype of each column.
To accommodate differences, such as extra columns returned from one table, but not from the other, you can add literal expressions in place of the "missing" columns.
The return of the extra src column is one way we can use to distinguish which query a row was returned by. It's not mandatory to return such a column, but it's something I often find useful. (The src column could be removed from each query, if it's not useful for your use case.)
Note that it's also possible to combine the results from more than two queries in this way, we'd just add another UNION ALL and another query.
The column names in the combined resultset are determined from the first query. The column names and aliases in the second query are ignored.
The ORDER BY applies to the entire set, and follows the last select.
Query should be linked via postID
F=feeds table, L=likes table, U1=usertable linked to owned feeds, U2=usertable linked to likes table
SELECT F.postTitle+' posted by '+ U1.username,'liked by'+U2.username
FROM likes L
LEFT JOIN feeds F on (F.postID=L.postID)
LEFT JOIN users U1 on (U1.userID=F.userID)
LEFT JOIN users U2 on (U2.userID=L.userID)
ORDER BY L.date,L.postID DESC
When you write SELECT * FROM feeds,likes... you are implicitly CROSS JOINing both tables. The engine will combine every record in each table with every record in the other. That is far from what you want.
I don't think you should be "linking" both tables, either. What you need, roughly speaking, is to get every post and every like, and then order that big set according to timestamps.
It sounds more like a UNION between two queries, and an ORDER BY applied to the whole UNION. UNIONs are never easy on the eye, by the way...
The thing with UNIONs is that both sub-queries need to return the same amount of columns. Not knowing exactly which columns you have, I'll show you one possible solution:
SELECT activity, timestamp FROM (
( SELECT CONCAT(u.name,' posted ',f.content) as activity, timestamp
FROM user u
JOIN feed f on (f.user_id=u.id)
WHERE f.deleted!=0
) UNION
( SELECT CONCAT(u.name, ' liked a post by ',u2.name) as activity, timestamp
FROM user u
JOIN likes l on (l.user_id=u.id)
JOIN feed f on (l.feed_id=f.id)
JOIN user u2 on (f.user_id=u2.id)
WHERE l.deleted!=0
)
) as whole_result
ORDER by timestamp desc
You should, of course, modify this to match your structure.
Hope this helps!
I think, it's better to use 3rd table, say, "actions", and insert to it real actions. Then just select rows from this table, joined to "posts" & "users" table.
When user posts articles, o likes an article, insert corresponding row to "actions" table.
actions table:
|id|action_name|user_id|post_id| date |
1 posted 3 3 5/7/2014
2 liked 5 3 5/7/2014
3 liked 4 3 6/7/2014
4 posted 5 6 7/7/2014
5 liked 3 6 7/7/2014
SELECT user_name a, post_title b, action_name c FROM actions c LEFT JOIN users a ON a.id=c.user_id LEFT JOIN posts b ON b.id = c.post_id ORDER BY c.date DESC LIMIT 10
Then, in loop, choose how to display this data, according to "action_name".
In such way you can expand your wall for other activities, +use indexes for better database performance.
I have this SQL query here that grabs the 5 latest news posts. I want to make it so it also grabs the total likes and total news comments in the same query. But the query I made seems to be a little slow when working with large amounts of data so I am trying to see if I can find a better solution. Here it is below:
SELECT *,
`id` as `newscode`,
(SELECT COUNT(*) FROM `likes` WHERE `type`="newspost" AND `code`=`newscode`) as `total_likes`,
(SELECT COUNT(*) FROM `news_comments` WHERE `post_id`=`newscode`) as `total_comments`
FROM `news` ORDER BY `id` DESC LIMIT 5
Here is a SQLFiddle as well: http://sqlfiddle.com/#!2/d3ecbf/1
I would recommend adding a total_likes and total_comments fields to the news table which gets incremented/decremented whenever a like and/or comment is added or removed.
Your likes and news_comments tables should be used for historical purposes only.
This strenuous counting should not be performed every time a page is loaded because that is a complete waste of resources.
You could rewrite this using joins, MySQL has known issues with subqueries, especially when dealing with large data sets:
SELECT n.*,
`id` as `newscode`,
COALESCE(l.TotalLikes, 0) AS `total_likes`,
COALESCE(c.TotalComments, 0) AS `total_comments`
FROM `news` n
LEFT JOIN
( SELECT Code, COUNT(*) AS TotalLikes
FROM `likes`
WHERE `type` = "newspost"
GROUP BY Code
) AS l
ON l.`code` = n.`id`
LEFT JOIN
( SELECT post_id, COUNT(*) AS TotalComments
FROM `news_comments`
GROUP BY post_id
) AS c
ON c.`post_id` = n.`id`
ORDER BY n.`id` DESC LIMIT 5;
The reason is that when you use a join as above, MySQL will materialise the results of the subquery when it is first needed, e.g at the start of this query, mySQL will put the results of:
SELECT post_id, COUNT(*) AS TotalComments
FROM `news_comments`
GROUP BY post_id
into an in memory table and hash post_id for faster lookups. Then for each row in news it only has to look up TotalComments from this hashed table, when you use a correlated subquery it will execute the query once for each row in news, which when news is large will result in a large number of executions. If the initial result set is small you may not see a performance benefit and it may be worse.
Examples on SQL Fiddle
Finally, you may want to index the relevant fields in news_comments and likes. For this particular query I think the following indexes will help:
CREATE INDEX IX_Likes_Code_Type ON Likes (Code, Type);
CREATE INDEX IX_newcomments_post_id ON news_comments (post_id);
Although you may need to split the first index into two:
CREATE INDEX IX_Likes_Code ON Likes (Code);
CREATE INDEX IX_Likes_Type ON Likes (Type);
First check for helping indexes on columns id, post_id and type,code.
I assume this is T-SQL, as that is what I am most familiar with.
First I would check indexes. If that looks good, then I'd check statement. Take a look at your query map to see how it's populating your result.
SQL works backward, so it starts with your last AND statement and goes from there. It'll group them all by code, and then type, and finally give you a count.
Right now, you're grabbing everything with certain codes, regardless of date. When you stated that you want the latest, I assume there is a date column somewhere.
In order to speed things up, add another AND to your WHERE and account for the date. Either last 24 hours, last week, whatever.
I am trying to query two tables: finished_events and flagged_events. 1st of all I need everything related to the company_id so
SELECT *
FROM finished_events
WHERE company_id=$id
ORDER by schedule, timestamp
I then changed this to:
SELECT * FROM finished_events
INNER JOIN flagged_events
ON finished_events.company_id=flagged_events.company_id
WHERE finished_events.company_id=$id
ORDER by finished_events.schedule, finished_events.timestamp
I have tried using FULL JOIN, LEFT JOIN, and RIGHT JOINs all unsuccessful. Specifically what I want is to get is a combined effort of the following code:
$sql = "SELECT *
FROM finished_events
WHERE company_id=$id
ORDER by schedule, time_stamp";
$flagged_sql = "SELECT *
FROM flagged_events
WHERE company_id=$id
ORDER by schedule, time_stamp";
The tables are a bit different so UNION won't work here. I can post dummy database entries but this won't be of too much help as I need all from both tables. The 2 links between the tables would be the company_id and the schedule columns. Essentially what is going on behind the scenes is timestamps being put into a different table to which I then process either into finished_events or flagged_events. Flagged events will need the user to do something about it until it is a finished event. So this script is generating the data for the GUI, hence why I need to query both tables and create an associative array of customer details then an array of events (from these 2 tables). So creating the assoc_array is no problem I just need to get this query to spit out all the events and order them correctly. Let me know if you need anything specific to solve this one, thanks :)
EDIT
SQL Fiddle: http://sqlfiddle.com/#!2/d4c30/1
this almost fixes it but not quite right, it repeats entries at the bottom
If I understood correctly, this may be useful for you:
SELECT a.* FROM (
SELECT *, 'finished' as event_type FROM finished_events
UNION
SELECT *, 'flagged' as event_type FROM flagged_events) a
ORDER BY a.schedule, a.time_stamp
I have two tables: "users" and "posts." The posts table has a 'post' column and a 'poster_id' column. I'm working on a PHP page that shows the latest posts by everyone, like this:
SELECT * FROM posts WHERE id < '$whatever' LIMIT 10
This way, I can print each result like this:
id: 43, poster_id:'4', post: hello, world
id: 44, poster_id:'4', post: hello, ward
id: 45, poster_id:'5', post: oh hi!
etc...
Instead of the id, I would like to display the NAME of the poster (there's a column for it in the 'users' table)
I've tried the following:
SELECT *
FROM posts
WHERE id < '$whatever'
INNER JOIN users
ON posts.poster_id = users.id LIMIT 10
Is this the correct type of join for this task? Before learning about joins, I would query the users table for each post result. The result should end up looking similar to this:
id: 43, poster_id:'4', name:'foo', post: hello, world
id: 44, poster_id:'4', name:'foo', post: hello, ward
id: 45, poster_id:'5', name:'fee', post: oh hi!
etc...
Thanks for helping in advance.
WHERE clause must come after the FROM clause.
SELECT posts.*, users.* // select your desired columns
FROM posts
INNER JOIN users ON posts.poster_id = users.id
WHERE id < '$whatever'
LIMIT 10
the SQL Order of Operation is as follows:
FROM clause
WHERE clause
GROUP BY clause
HAVING clause
SELECT clause
ORDER BY clause
UPDATE 1
For those column names that exists on both tables, add an ALIAS on them so it can be uniquely identified. example,
SELECT post.colName as PostCol,
users.colName as UserCol, ....
FROM ....
on the example above, both tables has column name colName. In order to get them both, you need to add alias on them so in your front end, use PostCol and UserCol to get their values.
Try:
SELECT *
FROM posts
INNER JOIN users ON posts.poster_id = users.id
WHERE posts.id < '$whatever'
LIMIT 10
Got the syntax a little incorrect.
Should be
SELECT * FROM posts
INNER JOIN users ON posts.poster_id = users.id
WHERE id < '$whatever' LIMIT 10
The answers already given tell you the main reason for your query not working at all (ie the WHERE clause should come after the JOIN clauses), however, I'd like to make a couple of additional points:
I would suggest using an OUTER JOIN for this. It probably won't make much difference, but in the event of a post record having an invalid poster_id, an INNER JOIN will mean the record is dropped from the results, whereas an OUTER JOIN will mean that the record is included, but the values from the users table will be null. I imagine you don't want to ever have an invalid poster_id on the posts table, but broken data does happen even in the best regulated system, and it is helpful in these cases to still get the data from the query.
I would strongly suggest not doing SELECT *, and instead itemising the fields you want to get back from the query. SELECT * has a number of problems, but it's particularly bad when you have multiple tables in the query, because if you have fields with the same name on both tables, (eg id), then it becomes very hard to distinguish which one you're working with, as your PHP recordset won't include the table reference. Itemising the fields may make your query string longer, but it won't make it any slower - if anything it'll be quicker - and it will be easier to work with in the long run.
Neither of these points are essential; the query will work without them (as long as you switch the WHERE clause to after the JOIN), but they may improve your query and hopefully also improve your understanding of SQL.