I'm having trouble building a query. I can do what I want in 3 different queries.
SELECT id FROM table1 WHERE url LIKE '%/$downloadfile'
put that in $url_id
SELECT item_id FROM table2 WHERE rel_id = '$url_id'"
put that in $item_id
SELECT rel_id FROM table2 WHERE rel_id = '$item_id' AND field_id = '42'"
put that in $user_id
But from reading examples on joins and inner joins I think there's a more elegant way. I cant wrap my brain around writing a better query (but would like to) I can describe how it should go:
table1
fields: id, url
table2
fields item_id, rel_id, field_id
I know the last part of table1.url (LIKE '%/$filename') with that I select table1.id.
table1.id is equal to one entry in table2.rel_id. So get that and select the table2.item_id.
In table2 there is another entry which has the same table2.item_id and it will have a table2.field_id = '42'
And finally the value I need is the table2.rel_id where the table2.field_id was 42.
I will fetch that value and put it in $user_id
Can this be done with one query using joins/inner joins?
SELECT url, second.rel_id AS user_id
FROM table1
INNER JOIN table2 AS first
ON table1.id=first.rel_id
INNER JOIN table2 AS second
ON first.item_id=second.rel_id
WHERE second.field_id='42'
AND table1.url LIKE '%/:downloadfile'
Sure, should be something like:
SELECT t2_second.rel_id
FROM table1 t1
INNER JOIN table2 t2_first ON t1.id = t2_first.rel_id
INNER JOIN table2 t2_second ON t2_second.rel_id = t1_first.item_it
WHERE
t1.url = '%/:filename' AND
t2_second.field_id = 42
You could even throw in a distinct so that each t2_second.rel_id is only returned once:
SELECT DISTINCT [...]
You might not need this, however, if t2_second.field_id = 42 will restrict the query to only return one row for each t2_second.rel_id
This the query that works for me, made one small change to Ignacio's answer:
SELECT url, second.rel_id AS user_id
FROM table1
INNER JOIN table2 AS first
ON table1.id=first.rel_id
INNER JOIN table2 AS second
ON first.item_id=second.item_id
WHERE second.field_id='42'
AND table1.url LIKE '%/:downloadfile'
Related
I have two table
Table 1:
Ensemble_ID
Target
Gene_length
miRNA
miRNA_length
mfe
pvalue
position
prediction
no_of_seeds
And in table2
Ensemble_ID
local_ID
I want to display the result in the following order,
Ensemble_ID, local_ID, Ensemble_ID, Target ,Gene_length, miRNA, miRNA_length, mfe, pvalue, position, prediction, no_of_seeds
But i could not join it .. Can some one help ??
This is what you are asking:
SELECT t1.Ensemble_ID AS Ensemble_ID1, t2.local_ID, t2.Ensemble_ID AS Ensemble_ID2,
t1.Target, t1.Gene_length, t1.miRNA,
t1.miRNA_length, t1.mfe, t1.pvalue, t1.position, t1.prediction, t1.no_of_seeds
FROM table1 t1, table2 t2
But it think you want something like this:
SELECT t2.local_ID, t2.Ensemble_ID, t1.Target, t1.Gene_length, t1.miRNA,
t1.miRNA_length, t1.mfe, t1.pvalue, t1.position, t1.prediction, t1.no_of_seeds
FROM table1 t1
INNER JOIN table2 t2 ON (t2.Ensemble_ID = t1.Ensemble_ID)
If you want to join table1 and table2 on Ensemble_ID there is no need to output it twice
I am trying to get a query using fields from 2 tables.
I need to query Table1 but only Table2 has the variable venue_location that I need to query.
Basically I need to count all records on Table1 where Table1.venue_location = $MyVariable.
Here is what I've put together but I believe I need to use Joins for this?
Table1
- venue_id
Table2
- venue_id,
- venue_location
SELECT * FROM Table1 WHERE table1.venue_id = table2.venue_id and table2.location = '$MyVariable'
How can I do a query for this?
Use the power of join table
SELECT * FROM Table1
JOIN Table2 USING(venue_id)
WHERE table2.location = '$MyVariable'
You can get back the count of rows with mysqli_num_rows() in PHP, or change le select by SELECT COUNT(*) AS nbRow FROM ... and check of value in nbRow column
You can join two tables on venue_id and then group it by venue_id where location is your $MyVariable.
Your final query will look like:
SELECT count(table2.venue_id)
FROM Table1
JOIN Table2 ON table1.venue_id = table2.venue_id
WHERE table2.location = '$MyVariable'
GROUP BY table2.venue_id
try this
SELECT Table1.venue_id, Table2.venue_location FROM Table1 INNER JOIN Table2
ON Table1.venue_id='$MyVariable';
Table1 Has Some data as Categories
Table2 Has Some data Which is Realated to table1 Categories
and the relation between two tables is cat_id from table1 and cat_ids from table2.
What I want is?
I need to display all fields in table1 and from table2 I need only the related content i.e id's present in cat_id(table1) and cat_ids(table2)
I am using a query like this select c.* ,cc.* from news_categories cc, news_content c where cc.cat_id = c.cat_ids group by cc.cat_id this gives only common data from table1 and table2.. i need common data and all categories from table1
can anyone help me?
You should use JOIN instead.
SELECT t1.*, GROUP_CONCAT(t2.content_id)
FROM table1 t1
LEFT JOIN table2 t2
ON t2.cat_ids = t1.cat_id
GROUP BY t1.cat_id
This is for all fields of both tables...
SELECT Table1.*, Table2.*
FROM Table1, Table2
WHERE Table1.cat_id = Table2.cat_ids
This is for all fields of Table1 and Content field of Table2...
SELECT Table1.*, Table2.full_content
FROM Table1, Table2
WHERE Table1.cat_id = Table2.cat_ids
you need to use outer join and this case left join .. Have a look at Documentation
I can do the following in 2 queries but want to make it simpler. Can this be combined in one query? If so how more efficient is it than doing two queries vs one?
query1: SELECT page_id, coupon_id from table_1 WHERE key = :key
query2: SELECT folder from table_2 WHERE page_id = table_1.page_id
For my final result I need to have a coupon_id from table_1, and a folder from table_2.
In query2 I need to use the page_id result from query1 to get the folder
Is there a simpler way to do this?
Use JOIN (LEFT, RIGHT or INNER is up to your needs):
SELECT
t1.page_id,
t1.coupon_id,
t2.folder
FROM
table_1 AS t1
LEFT JOIN table_2 AS t2 ON
t2.page_id = t1.page_id
WHERE
t1.key = :key
You will want to JOIN the tables on the page_id:
SELECT t1.page_id,
t1.coupon_id,
t2.folder
from table_1 t1
inner join table_2 t2
on t1.page_id = t2.page_id
WHERE key = :key
If you need help learning join syntax, here is a great visual explanation of joins.
I used an INNER JOIN which will return all rows that match between the two tables. If you want to return all rows from table_1
even if it doesn't have a matching row in table_2, then you would use a LEFT JOIN
SELECT
table_1.coupon_id AS coupon_id,
table_2.folder AS folder
FROM
table_1
INNER JOIN table_2 ON table_2.page_id = table_1.page_id
WHERE
table_1.key = :key
SELECT t1.page_id, t1.coupon_id, t2.folder
FROM table_1 t1 LEFT JOIN table_2 t2 ON (t1.page_id = t2.page_id)
WHERE t1.key = :key
This will be faster than two queries, how much depends on your data.
Try this please:
SELECT a.page_id, a.coupon_id, b.folder_id
from table_1 a
join table_2 b
ON a.page_id = b.page_id
WHERE a.key = :key
group by a.page_id
;
Ive looked at other questions and answers but still dont understand which brings me here.
I have one data base two tables. lets say table1 and table2 from database.
I'm looking to grab all the information from table1 and only one column from table2 that coincides with the correct row in table1.
Example which I know is wrong:
SELECT table1.*, table2.time_stamp FROM table1, table2
WHERE table1.ticket_id=$var AND table1.user_id = table2.user_id
Basically select data from table1 then use a value from the selected table to grab the related data from table2 and join them to output them as one mysql_query. Im sure its simple and has been asked before.
edit:
I dont receive an error. SQL just returns noting. log form of this would be:
$sqlResults = mysql_query("SELECT table1.* FROM table1 WHERE table1.ticket_id=$var")
while($rowResult = mysql_fetch_array( $sqlResults )) {
$userID = $rowResult['user_id'];
$sqlResults2 = mysql_query("SELECT table2.time_stamp FROM table2
WHERE table2.user_id=$userID")
}
I want to combine that into one sql statement so i dont have to hit table2 for every row table1 has
Use a JOIN to bind the rows from table2 to those from table1:
SELECT t1.*, t2.time_stamp FROM table1 t1
JOIN table2 t2 ON t1.user_id = t2.user_id
WHERE t1.ticket_id=$var