I have two tables. One for artists (artist_id, artist_name), one for tracks (track_id, artist_id, track_title).
I want to be able to handle queries like "better man pearl jam" but I'm having trouble thinking about the logic on how this would work. better man is the track title while pearl jam is the artist name.
We're currently using sphinx to handle our search engine (artists and tracks individually).
is there an efficient way to go about this?
I would think that if someone does a search that matches both track and artist, they're looking for the track. What is your desired behaviour in this case?
Based on your comment, your sphinx query should look like this then:
SELECT track_id, track_title, artists.artist_id, artist_name FROM tracks
LEFT JOIN artists WHERE artists.artist_id = tracks.artist_id;
If you're using PHP, your code would look something like:
$res = $sc->Query($searchString, "SphinxIndexName");
if (isset($res['matches']) && sizeof($res['matches']) > 0) {
ids = join(",", array_keys($res["matches"]));
$query = "SELECT track_id, track_title, artists.artist_id, artist_name FROM tracks
LEFT JOIN artists WHERE artists.artist_id = tracks.artist_id ORDER BY FIELD(track_id, $ids)";
// ... query MySQL and display results
}
else {
echo "no results";
}
Related
(Just started learning SQL a few days ago so sorry if this is a stupid question!)
I have three tables, Users, Addresses, and AddressCategories. Each User has multiple Addresses, but no more than 1 Address per AddressCategory. I would like to make a single query that searches for Users based on different criteria for each AddressCategory.
Table structure looks like:
Users:
id
1
2
AddressCategories:
category
HomeAddress
WorkAddress
Addresses:
userId category address
1 HomeAddress 1 Washington Street
1 WorkAddress 53 Elm Avenue
2 HomeAddress 7 Bernard Street
Let's say I want to search for all users whose home address contains the word "Street" and work address contains the word "Avenue". I can use the query:
SELECT * FROM Users
INNER JOIN Addresses a1 ON Users.id=a1.userId
INNER JOIN Addresses a2 ON Users.id=a2.userId
WHERE a1.category='HomeAddress' AND a1.address LIKE '%Street%'
AND a2.category='WorkAddress' AND a2.address LIKE '%Avenue%'
If I want to query across an arbitrary number of AddressCategories, I can dynamically build a query using the same principle above:
// dictionary of query parts
var q_parts = {HomeAddress: 'Street',
WorkAddress: 'Avenue'
...}
// build the query string piece by piece
let q_str1="", q_str2="";
let i=0;
for (q in q_parts) {
i++;
q_str1 += "INNER JOIN Addresses a${i} ON Users.id=a${1}.userId ";
q_str2 += (i==1) ? "WHERE " : "AND ";
q_str2 += "a${i}.category='${q}' AND a${i}.address LIKE '%${q_parts[q]}%' ";
}
// complete query string
let q_str = "SELECT * FROM Users "+q_str1+q_str2;
The way I'm doing it now works, but it's easy to make a mistake building the query string and the final string quickly becomes enormous as the number of categories grows. Seems like there must be a better way. What is the right way to perform such queries in MySQL? (Or is there a problem with how I've organized my tables?)
You can use this one for query building.
Official site: https://knexjs.org/
Npm link: https://www.npmjs.com/package/knex
A sample SQL for don't have to join many times. It is not tested, and just an idea.
You can use When/then in Where clause for verifying case by case. And finally, filter base on the total categories of a User (group by).
SELECT *
FROM
Users Inner Join
(SELECT userId,
count(category) AS categoryCount
WHERE address LIKE '%Street%' LIKE CASE
WHEN category = 'HomeAddress' THEN '%Street%'
WHEN category = 'WorkAddress' THEN '%Avenue%'
END
GROUP BY userId) a ON Users.id = a.userId
WHERE categoryCount = ? -- inject your count of all categories here, maybe get from another query
Hey I tried this thread but it doesn't work and i can't figure out why...
here's my SQL:
SELECT * FROM gone_items
LEFT JOIN items
ON gone_items.item_ID=items.ID
WHERE
gone_items.aus_ID='$ID'
ORDER BY items.name ASC
Now, I fetch that via PHP and have a $row and try another mysql to get the individual ID's of the gone_items table. But if i use $row['ID'] I get the ID of the items.ID not the one from gone_items.ID.
I tried setting the variable manually in the first query but it doesn't work.
I also tried this: MYSQL Left join A.table and b.table while retaining a.table id
Also didn't help me...
All I want is to retain the ID (Primary key) from the gone_items table..
Can anyone please tell me what I'm doing wrong ?
Love
Gram
EDIT
//Query for Joined infos
$sqlx="SELECT foto_res_ausgeliehene_geg.ID, foto_res_ausgeliehene_geg.aus_ID, foto_res_ausgeliehene_geg.geg_ID, foto_res_ausgeliehene_geg.zusaetzliches, foto_res_gegenstaende.ID, foto_res_gegenstaende.bezeichnung, foto_res_gegenstaende.seriennummer, foto_res_gegenstaende.interne_seriennummer, foto_res_gegenstaende.zusaetzliches FROM foto_res_ausgeliehene_geg
LEFT JOIN foto_res_gegenstaende
ON foto_res_ausgeliehene_geg.geg_ID=foto_res_gegenstaende.ID
WHERE
foto_res_ausgeliehene_geg.aus_ID='$ID'
ORDER BY foto_res_gegenstaende.bezeichnung ASC
";
$ergebnisx = mysqli_query($db,$sqlx);
while ($zeilex = mysqli_fetch_assoc($ergebnisx))
{
//Query for individual infos
$sqly="SELECT * FROM foto_res_ausgeliehene_geg
WHERE `geg_ID`='".$zeilex['ID']."'
AND `aus_ID`='$ID'
GROUP BY `geg_ID`
";
$ergebnisy = mysqli_query($db,$sqly);
while ($zeiley = mysqli_fetch_assoc($ergebnisy))
{};
Now I did select all items individually. The foto_res_ausgeliehene_geg.ID still merges with the foto_res_gegenstanede.ID due to the LEFT JOIN.
So if i access $zeilex['ID'] im getting the ID of foto_res_gegenstaende.ID.
Would it help if I rename the ID field in one of the tables into lets say item_ID ?
Thanks alot.
Love
Gram.
Instead of using select *, you should explicitly state what items you want to select. Else you can get conflicts with multiple id fields. In your case something like:
select gone_items.id, gone_items.column1, gone_items.column2, items.column1, items.column2
It is also considered good practice, to limit the amount of data there is being selected. But is meanwhile also a highly debateable what is the right way. Performance issue in using SELECT *?
WORKS!
I simply renamed one of the Primary ID keys to something else, in this case, one of them got ID -> item_ID. The other one still is ID that way the left join won't merge them.
yolo
EDIT
WORKING CODE
$sqlx="SELECT foto_res_ausgeliehene_geg.item_ID, foto_res_ausgeliehene_geg.aus_ID, foto_res_ausgeliehene_geg.geg_ID, foto_res_ausgeliehene_geg.zusaetzliches, foto_res_gegenstaende.ID, foto_res_gegenstaende.bezeichnung, foto_res_gegenstaende.seriennummer, foto_res_gegenstaende.interne_seriennummer, foto_res_gegenstaende.zusaetzliches FROM foto_res_ausgeliehene_geg
LEFT JOIN foto_res_gegenstaende
ON foto_res_ausgeliehene_geg.geg_ID=foto_res_gegenstaende.ID
WHERE
foto_res_ausgeliehene_geg.aus_ID='$ID'
ORDER BY foto_res_gegenstaende.bezeichnung ASC
";
$ergebnisx = mysqli_query($db,$sqlx);
while ($zeilex = mysqli_fetch_assoc($ergebnisx))
{
//Query for individual infos
$sqly="SELECT * FROM foto_res_ausgeliehene_geg
WHERE `item_ID`='".$zeilex['item_ID']."'
";
$ergebnisy = mysqli_query($db,$sqly);
while ($zeiley = mysqli_fetch_assoc($ergebnisy))
{
I have a database representing something like a bookstore. There's a table containing the categories that books can be in. Some categories are defined simply using another table that contains the category-item relationships. But there are also some categories that can be defined programmatically -- a category for a specific author can be defined using a query (SELECT item_id FROM items WHERE author = "John Smith"). So my categories table has a "query" column; if it's not null, I use this to get the items in the category, otherwise I use the category_items table.
Currently, I have the application (PHP code) make this decision, but this means lots of separate queries when we iterate over all the categories. Is there some way to incorporate this dynamic SQL into a join? Something like:
SELECT c.category, IF(c.query IS NULL, count(i.items), count(EXECUTE c.query)
FROM categories c
LEFT OUTER JOIN category_items i
ON c.category = i.category
EXECUTE requires a prepared statement, but I need to prepare a different statement for each row. Also, EXECUTE can't be used in expressions, it's just a toplevel statement. Suggestions?
What happens when you want to list books by publisher? Country? Language? You'd have to throw them all into a single "category_items" table. How would you pick which dynamic query to execute? The query-within-a-query method is not going to work.
I think your concept of "category" is too broad, which is resulting in overly complicated SQL. I would replace "category" to represent only "genre" (for books). Genres are defined in their own table, and item_genres connects them to the items table. Books-by-author and books-by-genre should just be separate queries at the application level, rather than trying to do them both with the same (sort of) query at the database/SQL level. (If you have music as well as books, they probably shouldn't all be stored in a single "items" table because they're different concepts ... have different genres, author vs. artist, etc.)
I know this does not really solve your problem in the way you'd like, but I think you'll be happier not trying to do it that way.
Here's how I finally ended up solving this in the PHP client.
I decided to just keep the membership in the category_items table, and use the dynamic queries during submission to update this table.
This is the function in my script that's called to update an item's categories during submission or updating. It takes a list of user-selected categories (which can only be chosen from categories that don't have dynamic queries), and using this and the dynamic queries it figures out the difference between the categories that an item is currently in and the ones it should be in, and inserts/deletes as necessary to get them in sync. (Note that the actual table names in my DB are not the same as in my question, I was using somewhat generic terms.)
function update_item_categories($dbh, $id, $requested_cats) {
$data = mysql_check($dbh, mysqli_query($dbh, "select id, query from t_ld_categories where query is not null"), 'getting dynamic categories');
$clauses = array();
while ($row = mysqli_fetch_object($data))
$clauses[] = sprintf('select %d cat_id, (%d in (%s)) should_be_in',
$row->id, $id, $row->query);
if (!$requested_cats) $requested_cats[] = -1; // Dummy entry that never matches cat_id
$requested_cat_string = implode(', ', $requested_cats);
$clauses[] = "select c.id cat_id, (c.id in ($requested_cat_string)) should_be_in
from t_ld_categories c
where member_type = 'lessons' and query is null";
$subquery = implode("\nunion all\n", $clauses);
$query = "select c.cat_id cat_id, should_be_in, (member_id is not null) is_in
from ($subquery) c
left outer join t_ld_cat_members m
on c.cat_id = m.cat_id
and m.member_id = $id";
// printf("<pre>$query</pre>");
$data = mysql_check($dbh, mysqli_query($dbh, $query), 'getting current category membership');
$adds = array();
$deletes = array();
while ($row = mysqli_fetch_object($data)) {
if ($row->should_be_in && !$row->is_in) $adds[] = "({$row->cat_id}, $id)";
elseif (!$row->should_be_in && $row->is_in) $deletes[] = "(cat_id = {$row->cat_id} and member_id = $id)";
}
if ($deletes) {
$delete_string = implode(' or ', $deletes);
mysql_check($dbh, mysqli_query($dbh, "delete from t_ld_cat_members where $delete_string"), 'deleting old categories');
}
if ($adds) {
$add_string = implode(', ', $adds);
mysql_check($dbh, mysqli_query($dbh, "insert into t_ld_cat_members (cat_id, member_id) values $add_string"),
"adding new categories");
}
}
Good evening guys,
I'm a newbie to web programming and I need your help to solve a problem inherent to SQL query.
The database engine I'm using is MySQL and I access it via PHP, here I'll explain a simplified version of my database, just to fix ideas.
Let's suppose to work with a database containing three tables: teams, teams_information, attributes. More precisely:
1) teams is a table containing some basic information about italian football teams (soccer, not american football :D), it is formed by three fields: 'id' (int, primary key), 'name' (varchar, team name), nickname (Varchar, team nickname);
2) attributes is a table containing a list of possible information about a football team, such as city (the city where team plays its home match), captain (team captain's fullname), f_number (number of fans) and so on. This table is formed by three fields: id (int, primary key), attribute_name (varchar, an identifier for the attribute), attribute_desc (text, an explanation of the meaning of attribute). Each record of this table represents a single possible attribute of a football team;
3) teams_information is a table where some information, about teams listed in team table, are available. This table contains three fields: id (int, primary key), team_id (int, a foreign key which identifies a team), attribute_id (int, a foreign key which identifies one of the attributes listed in attributes table), attribute_value (varchar, the value of the attribute). Each record represents a single attribute of a single team. In general, different teams will have a different number of information, so for some teams a large number of attributes will be available while for other teams only a small number of attributes will be available.
Note that relation between teams and teams_information is one to many and the same relation exists between attributes and teams_information
Well, given this model my purpose is to realize a grid (maybe with ExtJS 4.1) to show user the list of italian football team, each record of this grid will represent a single football team and will contain all possible attributes: some fields may be empty (because, for considered team, the correspondent attribute is unknown), while the others will contain the values stored in teams_information table (for the considered team).
According to the above grid's field are: id, team_name and a number of fields to represent all the different attributes listed in 'attributes' table.
My question is: can I realize such a grid by using a SINGLE SQL query (maybe a proper SELECT query, to fetch all data I need from database tables) ?
Can anyone suggest me how to write a similar query (if it exists) ?
Thanks in advance for helping me.
Regards.
Enrico.
The short answer to your question is no, there is no simple construct in MySQL to achieve the result set you are looking for.
But it is possible to carefully (painstakingly) craft such a query. Here is an example, I trust you will be able to decipher it. Basically, I'm using correlated subqueries in the select list, for each attribute I want returned.
SELECT t.id
, t.name
, t.nickname
, ( SELECT v1.attribute_value
FROM team_information v1
JOIN attributes a1
ON a1.id = v1.attribute_id AND a1.attribute_name = 'city'
WHERE v1.team_id = t.id ORDER BY 1 LIMIT 1
) AS city
, ( SELECT v2.attribute_value
FROM team_information v2 JOIN attributes a2
ON a2.id = v2.attribute_id AND a2.attribute_name = 'captain'
WHERE v2.team_id = t.id ORDER BY 1 LIMIT 1
) AS captain
, ( SELECT v3.attribute_value
FROM team_information v3 JOIN attributes a3
ON a3.id = v3.attribute_id AND a3.attribute_name = 'f_number'
WHERE v3.team_id = t.id ORDER BY 1 LIMIT 1
) AS f_number
FROM teams t
ORDER BY t.id
For 'multi-valued' attributes, you'd have to pull each instance of the attribute separately. (Use the LIMIT to specify whether you are retrieving the first one, the second one, etc.)
, ( SELECT v4.attribute_value
FROM team_information v4 JOIN attributes a4
ON a4.id = v4.attribute_id AND a4.attribute_name = 'nickname'
WHERE v4.team_id = t.id ORDER BY 1 LIMIT 0,1
) AS nickname_1st
, ( SELECT v5.attribute_value
FROM team_information v5 JOIN attributes a5
ON a5.id = v5.attribute_id AND a5.attribute_name = 'nickname'
WHERE v5.team_id = t.id ORDER BY 1 LIMIT 1,1
) AS nickname_2nd
, ( SELECT v6.attribute_value
FROM team_information v6 JOIN attributes a6
ON a6.id = v6.attribute_id AND a6.attribute_name = 'nickname'
WHERE v6.team_id = t.id ORDER BY 1 LIMIT 2,1
) AS nickname_3rd
I use nickname as an example here, because American soccer clubs frequently have more than one nickname, e.g. Chicago Fire Soccer Club has nicknames: 'The Fire', 'La Máquina Roja', 'Men in Red', 'CF97', et al.)
NOT AN ANSWER TO YOUR QUESTION, BUT ...
Have I mentioned numerous times before, how much I dislike working with EAV database implementations? What should IMO be a very simple query turns into an overly complicated beast of a potentially light dimming query.
Wouldn't it be much simpler to create a table where each "attribute" is a separate column? Then queries to return reasonable result sets would look more reasonable...
SELECT id, name, nickname, city, captain, f_number, ... FROM team
But what really makes me shudder is the prospect that some developer is going to decide that the LDQ should be "hidden" in the database as a view, to enable the "simpler" query.
If you go this route, PLEASE PLEASE PLEASE resist any urge you may have to store this query in the database as a view.
I'm going to take a slightly different route. Spencer's answer is fantastic, and it addresses the issue quite well, but there's still a large underlying problem.
The data that you are trying to display on the site is over-normalized in the database. I won't elaborate, since, again, Spencer's answer highlights the issue pretty well.
Rather, I'd like to recommend a solution that denormalizes the data a bit.
Convert all of your Team data into a single table with many columns. (If there is Player data that isn't covered in the question, that would be a second table, but I'll gloss over that for now.)
Sure, you'll have a whole bunch of columns, and a lot of the columns might be NULL for a lot of the rows. It's not normalized, and it's not pretty, but here's the huge advantage that you gain.
Your query becomes:
SELECT * FROM Teams
That's it. That gets displayed right to the website and you are done. You might have to go out of your way to realize this schema, but it would be totally worth the time investment.
I think what you're saying is that you want the rows in the attributes table to appear as columns in the result recordset. If this is correct, then then in SQL you would use PIVOT.
A quick search on SO seems to indicate that there is no PIVOT equivalent in MySql.
I wrote a simple PHP script to generalize spencer's idea to solve my issue.
Here's the code:
<?php
require_once('includes/db.config.php'); //this file performs connection to mysql
/*
* Following function requires a table name ($table)
* and a number of service fields ($num). Given those parameters
* it returns the number of table fields (excluding service fields).
*/
function get_fields_number($table,$num,$conn)
{
$query = "SELECT * FROM $table";
$result = mysql_query($query,$conn);
return mysql_num_fields($result)-$num; //remember there are $num service fields
}
/*
* Following function requires a table name ($table) and an array
* containing a list of service fields names. Given those parameters,
* it returns the list of field names. That list is contained within an array and
* service fields are excluded.
*/
function get_fields_name($table,$service,$conn)
{
$query = "SELECT * FROM $table";
$result = mysql_query($query,$conn);
$name = array(); //Array to be returned
for ($i=0;$i<mysql_num_fields($result);$i++)
{
if(!in_array(mysql_field_name($result,$i),$service))
{
//currently selected field is not a service field
$name[] = mysql_field_name($result,$i);
}
}
return $name;
}
//Below $conn is db connection created in 'db.config.php'
$query = "SELECT `name` FROM `detail_arg` WHERE visibility = 0";
$res = mysql_query($query,$conn);
if($res===false)
{
$err_msg = mysql_real_escape_string(mysql_error($conn));
echo "{success:false,data:'".$err_msg."'}";
die();
}
$arg = array(); //list of argument names
while($row = mysql_fetch_assoc($res))
{
$arg[] = $row['name'];
}
//Following function writes the select subquery which is
//necessary to build a column containing a single attribute.
function make_subquery($attribute) //$attribute contains attribute name
{
$query = "";
$query.="(SELECT incident_detail.arg_value ";
$query.="FROM incident_detail ";
$query.="INNER JOIN detail_arg ";
$query.="ON incident_detail.arg_id = detail_arg.id AND detail_arg.name='".$attribute."' ";
$query.="WHERE incident.id = incident_detail.incident_id) ";
$query.="AS $attribute";
return $query;
}
/*
echo make_subquery("date"); //debug code
*/
$subquery = array(); //list of subqueries
for($i=0;$i<count($arg);$i++)
{
$subquery[] = make_subquery($arg[$i]);
}
$query = "SELECT "; //final query containing subqueries
$fields = get_fields_name("incident",array("id","visibility"),$conn);
//list of 'incident' table's fields
for($i=0;$i<count($fields);$i++)
{
$query.="incident.".$fields[$i].", ";
}
//insert the subqueries
$sub = implode($subquery,", ");
$query .= $sub;
$query.=" FROM incident ORDER BY incident.id";
echo $query;
?>
I have two tables: Users and Groups
In my table "Users", there is a column called "ID" for all the user ids.
In my table "Groups" there is a column called "Participants", fields in this column are filled with all the user ids like this "PID_134,PID_489,PID_4784," - And there is a column "ID" that identifies a specific group.
Now what i want to do, i want to create a menu that shows all the users that are not yet in this particular group.
So i need to get all the user ids, that are not yet in the Participants column of a group with a particular ID.
It would be cool if there was a single mysql query for that - But any PHP + MySQL solutions are okay, too.
How does that work? Any guesses?
UPDATE:
i know, that's not code, but is there a way I could do something like this that would return me a list of all the users?
SELECT *
FROM users, groups
WHERE groups.participants NOT LIKE '%PID_'users.id'%' AND groups.id = 1;
Something like this. You just get rid of "PID_" part of ID.
SELECT * FROM [users] WHERE [id] NOT IN
(SELECT replace(id,'PID_','') FROM groups WHERE group_name='group1')
Group1 would be your variable - group id/name of menu that you've opened.
You can select from multiple tables as shown below:
SELECT * from users, groups WHERE users.id != groups.participants AND groups.id = 1;
This will list all users who are not in group id 1; A more elegant solution can be found by using joins, but this is simple and will do the trick.
I believe something like that should help:
SELECT * FROM users WHERE users.id NOT IN (SELECT groups.participants FROM groups)
But this works only if your DB is normalized. So for your case I see only PHP + MySQL solution. Not very elegant, but it does the job.
<?php
$participants_array = mysql_query("SELECT participants FROM groups");
$ids = array();
while ($participant = mysql_fetch_assoc($participants_array))
{
$id = explode(',', $participant['participant']);
foreach ($id as $instance)
{
if (!in_array($instance, $ids)) $ids[] = $instance;
}
}
$participants = implode(',', $ids);
$result = mysql_query("SELECT * FROM users WHERE id NOT IN ( $participants )");
But I highly recommend normalizing the database.