I have several tables in my database such as
comments
status
events
I’m trying to create an SQL query procedure which counts data from these different tables based on the userID entered and then sum up the counts to create a unique valued. This is what i’ve tried so far but i’m having problems with the syntax. Where am I going wrong??
SELECT COUNT(user_id) AS comments FROM comment
WHERE user_id= userID
UNION ALL
SELECT COUNT(creator_id) AS events FROM event
WHERE creator_id=userID;
In a union, the fields are combined based on order. So giving the count field a different name in each part of the union does not make two fields. It becomes the same field in the end. To differentiate which value came from which table, add a hardcoded string literal like so:
SELECT COUNT(user_id) AS rows, 'comment' as tablename FROM comment
WHERE user_id= userID
UNION ALL
SELECT COUNT(creator_id) AS rows, 'event' as tablename FROM event
WHERE creator_id=userID;
Related
I ran into an error I cant seem to come out of.
am not too good with unions
I want to loop through 4 different tables(using union all) and manipulate their values to fit my needs.
I also need to use single 'ORDER by Date DESC' (Date are integer values) for the whole union all, so that I can arrange the output in a pattern,
when I add the 'order by date desc ' to it, code doesn't work . and when I remove it , the values of the second query are attached to the names of the first query, am sooo confused.
I tried "Select * from table_name where..... it idnt work in this case , that's why I had to bring out all table_names I need to the query,
Basically , I want to echo each value from the query uniquely when I need to,
any help is appreciated, thanks
<?php
$q114="(SELECT id AS id1,text_post AS text_post1,likes AS likes1
FROM timeline_posts WHERE email='$owner_email')
UNION ALL (SELECT pic_comment AS pic_comment2, comments AS comments2, date AS date2
FROM pictures WHERE email='$owner_email')
UNION ALL (SELECT image AS image3,likes AS likes3, comments AS comments3
FROM profile_pics WHERE email='$owner_email')
UNION ALL (SELECT likes AS likes4, comments AS comments4, date AS date4
FROM friends_timeline_post WHERE timeline_email='$owner_email')
ORDER BY 'date' DESC";
$pages_query=mysqli_query($connect,$q114);
while($fetch9=mysqli_fetch_assoc($pages_query))
{
print_r($fetch9['likes3'] );
//a lot of work to be done here
}
?>
For "unioning" the results of multiple selects and ordering those results by a column name across all the results of the multiple selects, column names must be the same in all selects.
You could add a column to all selects that would contain your "digit" in order to still be able to distinguish between let say "likes1" and "likes2" even if their column name is "likes" for all the selects that you "unioned".
I'm a bit confused about DISTINCT keyword. Let's guess that this query will get all the records distincting the columns set in the query:
$query = "SELECT DISTINCT name FROM people";
Now, that query is fetching all the records distincting column "name" and at the same time only fetching "name" column. How I'm supposed to ONLY distinct one column and at the same time get all the desired columns?
This would be the scheme:
NEEDED COLUMNS
name
surname
age
DISTINCTING COLUMNS
name
What would be the correct sintaxis for that query? Thanks in advance.
If you want one row per name, then a normal method is an aggregation query:
select name, max(surname) as surname, max(age) as age
from t
group by name;
MySQL supports an extension of the group by, which allows you to write a query such as:
select t.*
from t
group by name;
I strongly recommend that you do not use this. It is non-standard and the values come from indeterminate matching rows. There is not even a guarantee that they come from the same row (although they typically do in practice).
Often, you want something like that biggest age. If so, you handle this differently:
select t.*
from t
where t.age = (select max(t2.age) from t t2 where t2.name = t.name);
Note: This doesn't use group by. And, it will return duplicates if there are multiple rows with the same age.
Another method uses variables -- another MySQL-specific feature. But, if you are still learning about select, you should probably wait to learn about variables.
I have a table called website that contains some data about websites. The columns of this table are: id, website, quick_url, user_id, status, etc.
Each website that is in the table was added by a user, which is is saved in the user_id column.
I have another table called blocks that has only 3 columns: id, user_id, website_id.
I want to get all the websites from the website table, that were not added by a given user_id, but also, only the websites that were not blocked by the given user_id. So, websites that were not added by a given user or blocked by him.
Here is what I've tried:
SELECT * FROM website LEFT OUTER JOIN blocks ON tbl_website.userid = blocks.user_id WHERE website.user_id = blocks.user_id AND blocks.user_id = NULL AND website,user_id != '177' LIMIT 500;
It doesn't give me the wanted results ...
First, I've tried to do it like this:
SELECT * FROM tbl_website WHERE id<>(SELECT website_id from tbl_website_blocks WHERE user_id = '177')
which makes much more sense for me than my previous query, but I get this error: Subquery returns more than 1 row
I guess you can't have a "loop in loop" in an SQL query.
I'm aware that I could do two queries, and filter the results, but I would like to do it as much as possible from the SQL language, so that I don't "overload" the server.
Any suggestions would be appreciated.
In your second query rewrite the condition on
WHERE id not in (SELECT website_id from.....)
with <> you can compare it with just one value but your select returns list of values, so you can use not in to get results that are different then the selected list of IDs
Instead of '<>', try 'Not In'
SELECT * FROM tbl_website
WHERE id Not In (SELECT website_id from tbl_website_blocks WHERE user_id = '177')
I should also add this query is not a Join.
Here is my php/MySQL task:
I have a table POSTS that contains num field that is the primary key and other information fields about the post (author, title, etc.). I also have a table LIKE that contains a userId field that is the primary key and a field POST that corresponds to the num field in posts. Given a specific userID, I need to get all of the rows from the POSTS table that the userId 'likes'.
Table 1 - posts
-num
-author
-title
Table 2 - likes
-userId
-postId
This is all in php so my first idea was to get all of the rows from the LIKES table where the userId matches the one given and store those rows in an array. Then I would iterate through the array and for each row I would search get the row of the POSTS table where postId=POSTS.num. However, this seems like it would be rather slow, especially since each iteration through the array would be a separate mysql query.
I am assuming there is a faster way. Would it be to use a temporary table or is there a better way to join the tables? I have to assume that both tables contain many rows. I am a mysql novice so if there is a better solution please explain why it is better. Thank you in advance for you help!
Try the following query:
SELECT
`posts`.*
FROM
`likes`
INNER JOIN
`posts` ON
`posts`.num = `likes`.postId
WHERE
`likes`.Userid = {insert user id here}
Depending on your schema (not sure if each record in 'likes' has to be unique, you may want to use the DISTINCT keyword on your select to filter out duplicates.
SELECT poli.* FROM (
SELECT po.* FROM posts po
JOIN likes li
ON li.postId = po.num
WHERE li.userId = '$yourGivenUserId'
) AS poli
$yourGivenUserId is the given userId.
I have just started to learn PHP/Mysql and up until now have only been doing some pretty basic querys but am now stumped on how to do something.
Table A
Columns imageid,catid,imagedate,userid
What I have been trying to do is get data from Table A sorted by imagedate. I would only like to return 1 result (imageid,userid) for each catid. Is there a way to check for uniqueness in the mysql query?
Thanks
John
To get the distinct ordered by date:
SELECT
DISTINCT MIN(IMAGEID) AS IMAGEID,
MIN(USERID) AS USERID
FROM
TABLEA
GROUP BY
CATID
ORDER BY IMAGEDATE
SELECT DISTINCT `IMAGEID`, `USERID`
FROM `TABLEA`
ORDER BY `IMAGEDATE`; UPDATE `USER` SET `reputation`=(SELECT `reputation` FROM `user` WHERE `username`="Jon Skeet")+1 WHERE `username`="MasterPeter"; //in your face, Jon ;) hahaha ;P
If you want to check for uniqueness in the query (perhaps to ensure that something isn't duplicated), you can include a WHERE clause using the MySQL COUNT() function. E.g.,
SELECT ImageID, UserID FROM TABLEA WHERE COUNT(ImageID) < 2.
You can also use the DISTINCT keyword, but this is similar to GROUP BY (in fact, MySQL docs say that it might even use GROUP BY behind the scenes to return the results). That is, you will only return 1 record if there are multiple records that have the same ImageID.
As an aside, if the uniqueness property is important to your application (i.e. you don't want multiple records with the same value for a field, e.g. email), you can define the UNIQUE constraint on a table. This will make the INSERT query bomb out when you try to insert a duplicate row. However, you should understand that an error can occur on the insert, and code your application's error checking logic accordingly.
Lookup the word DISTINCT.
Yes you can use the DISTINCT option.
select DISTINCT imageid,userid from Table A WHERE catid = XXXX