I have several queries that have a same filter.
For example:
Filter:
$criteria = "AND id_student = 1 AND id_major = 2 ";
Query 1:
$query1 = "SELECT * FROM student AS t0
LEFT JOIN major AS t1 ON t0.id_major = t1.id
WHERE 1=1 ";
Query 2:
$query2 = "SELECT * FROM lecturer AS t0
LEFT JOIN major AS t1 ON t0.id_major = t1.id
LEFT JOIN student AS t2 ON t2.id_major = t1.id
WHERE 1=1 "
It will be run as
$query1.$criteria
and
$query2.$criteria
As you can see, this will yield a query error, since id_major is ambiguous.
My problem is, that this query is very big in number, so I prefer not to hard-code and change the $criteria and $query individually.
I've tried to change the $criteria into
$criteria = "AND student.id_student = 1 AND major.id_major = 2 ";
But it does no better, it gave me errors of "did you mean t0", "did you mean t2", etc.
So, can I do something like, get an alias of a table? So I can put it in the $criteria
$criteria = "AND (get-alias-code).id_student = 1 AND (get-alias-code).id_major = 2 ";
Or any other method?
I am not the primary developer of this program, just a bug-fixer so I cannot change much of this program (because those queries may affect another page).
Use the aliases you have for your tables already, and set the criteria to be
$criteria = "AND t0.`id_student`='1' AND t1.`id_major`='2' ";
I strongly recommend using backtics and ticks as well, it helps avoiding funny mistakes with table or field names like 'order' :)
Then all you need to ensure is that the table that needs the criteria applied gets the correct alias every time
Edit:
Hm...alternatively, you can remove aliasing from all queries.
I honestly don't think that there's any mysql feature to get the aliases for tables. You could run a string analyser code snippet to find them (knowing all table names it may not even be hard to do) but that looks like a very ugly solution IMHO.
I don't know away to handle it on sql but you can handle it with on array for example
$alias[1]["student"] = "t0"; // it means on query 1 your alias for student is t0
now you can use this variable on your filter
$criteria = "AND ".$alias[1]["student"].".id_student = 1 AND ".$alias[1]["major"].".id_major = 2 ";
I think it's one of fast ways to change your filter without changing all of queries.
hope It helps
Wrap the whole thing in an outer query like this:
"SELECT * FROM (".$query1.") a ".$criteria;
Assuming of course that the original query didn't create multiple columns with the same name, you can now reference them without the alias.
Related
I have almost thousands of data to display for my reports and it makes my browser lags due to the heavy data. I think that my query is the real problem. How can I optimized my query? is there something that I should add in my query?
I am using Xampp which supports PHP7.
SELECT
`payroll_billed_units`.`allotment_code`,
`payroll_billed_units`.`category_name`,
`payroll_billed_units`.`ntp_number`,
`payroll_billed_units`.`activity`,
`payroll_billed_units`.`regular_labor`,
`payroll_sub`.`block_number`,
(SELECT
GROUP_CONCAT(DISTINCT `lot_number` SEPARATOR ', ')
FROM
`payroll_billed_units` `lot_numbers`
WHERE
`lot_numbers`.`allotment_code` = `payroll_billed_units`.`allotment_code`
AND `lot_numbers`.`category_name` = `payroll_billed_units`.`category_name`
AND `lot_numbers`.`ntp_number` = `payroll_billed_units`.`ntp_number`
AND `lot_numbers`.`activity` = `payroll_billed_units`.`activity`) AS `lot_numbers`,
(SELECT
COUNT(`billed`.`ntp_id`)
FROM
`regular_ntp` `billed`
WHERE
`billed`.`allotment_code` = `payroll_billed_units`.`allotment_code`
AND `billed`.`category_name` = `payroll_billed_units`.`category_name`
AND `billed`.`ntp_number` = `payroll_billed_units`.`ntp_number`
AND `billed`.`activity` = `payroll_billed_units`.`activity`) AS `billed`,
(SELECT
COUNT(`approved`.`id`)
FROM
`payroll_billed_units` `approved`
WHERE
`approved`.`allotment_code` = `payroll_billed_units`.`allotment_code`
AND `approved`.`category_name` = `payroll_billed_units`.`category_name`
AND `approved`.`ntp_number` = `payroll_billed_units`.`ntp_number`
AND `approved`.`activity` = `payroll_billed_units`.`activity`) AS `approved`
FROM
`payroll_billed_units`
JOIN payroll_transaction ON payroll_billed_units.billing_number =
payroll_transaction.billing_number
JOIN payroll_sub ON payroll_transaction.billing_number =
payroll_sub.billing_number
WHERE payroll_billed_units.billing_date = '2019-02-13'
AND payroll_transaction.contractor_name = 'Roy Codal' GROUP BY allotment_code, category_name, activity
I was expecting that it will load or display all my data.
The biggest problem are the dependendt sub-selects, they are responsible for a bad performance. A sub-select will be executed for EVERY ROW of the outer query. And if you cascade subs-selects, you'll quickly have a query run forever.
If any of the parts would yield only 5 resultsets, 3 sub-select would mean that the database has to run 625 queries (5^4)!
Use JOINs.
Several of your tables need this 'composite' index:
INDEX(allotment_code, category_name, ntp_number, activity) -- in any order
payroll_transaction needs INDEX(contractor_name), though it may not get used.
payroll_billed_units needs INDEX(billing_date), though it may not get used.
For further discussion, please provide SHOW CREATE TABLE for each table and EXPLAIN SELECT ...
Use simply COUNT(*) instead of COUNT(foo). The latter checks the column for being not-NULL before including it. This is usually not needed. The reader is confused by thinking that there might be NULLs.
Your GROUP BY is improper because it is missing ntp_number. Read about the sql_mode of ONLY_FULL_GROUP_BY. I bring this up because you can almost get rid of some of those subqueries.
Another issue... Because of the "inflate-deflate" nature of JOIN with GROUP BY, the numbers may be inflated. I recommend you manually check the values of the COUNTs.
Heyy i think i need to do a query inside a query.
Here is what i tried to do(it seems to work but it takes forever to load) :
$query="SELECT * FROM Table1";
$results=mysql_query($query);
while($row=mysql_fetch_array($results)){
$bnr=$row['COL 1'];
$usg=$row['COL 19'];
echo"$bnr hat $usg <br /> ";
$sqlupdate="UPDATE TABLE_1
SET
Usg='$usg'
WHERE
bnr = '$bnr'";
mysql_query($sqlupdate);
}
Yes, updating many rows individually will take a long time regardless of whether you're doing it inside another query.
But certainly running two queries on the same database, at the same time will not help the situation at all!
That said, the good news is that in your example you're able to perform the update entirely on the server using an update with a join.
UPDATE TABLE_1 as TDest
INNER JOIN TABLE1 as TSrc
ON TDest.bnr = TSrc.`COL 1`
SET TDest.Usg = TSrc.`COL 19`
I think the MySQL query that you want is:
update tdest t1 join
tdest t2
on t1.bnr = t2.`Col 1`
set t1.usg = t2.`Col 19`;
I have a situation where lets say i'm trying to get the information about some food. Then I need to display all the information plus all the ingredients in that food.
With my query, i'm getting all the information in an array but only the first ingredient...
myFoodsArr =
[0]
foodDescription = "the description text will be here"
ratingAverage = 0
foodId = 4
ingredient = 1
ingAmount = 2
foodName = "Awesome Food name"
typeOfFood = 6
votes = 0
I would like to get something back like this...
myFoodsArr =
[0]
foodDescription = "the description text will be here"
ratingAverage = 0
foodId = 4
ingArr = {ingredient: 1, ingAmount: 4}, {ingredient: 3, ingAmount: 2}, {ingredient: 5, ingAmount: 1}
foodName = "Awesome Food name"
typeOfFood = 6
votes = 0
This is the query im working with right now. How can I adjust this to return the food ID 4 and then also get ALL the ingredients for that food? All while at the same time doing other things like getting the average rating of that food?
Thanks!
SELECT a.foodId, a.foodName, a.foodDescription, a.typeOfFood, c.ingredient, c.ingAmount, AVG(b.foodRating) AS ratingAverage, COUNT(b.foodId) as tvotes
FROM `foods` a
LEFT JOIN `foods_ratings` b
ON a.foodId = b.foodId
LEFT JOIN `foods_ing` c
ON a.foodId=c.foodId
WHERE a.foodId=4
EDIT:
Catcall introduced this concept of "sub queries" I never heard of, so I'm trying to make that work to see if i can do this in 1 query easily. But i just keep getting a return false. This is what I was trying with no luck..
//I changed some of the column names to help them be more distinct in this example
SELECT a.foodId, a.foodName, a.foodDescription, a.typeOfFood, AVG(b.foodRating) AS ratingAverage, COUNT(b.foodId) as tvotes
FROM foods a
LEFT JOIN foods_ratings b ON a.foodId = b.foodId
LEFT JOIN (SELECT fId, ingredientId, ingAmount
FROM foods_ing
WHERE fId = 4
GROUP BY fId) c ON a.foodId = c.fId
WHERE a.foodId = 4";
EDIT 1 more thing related to ROLANDS GROUP_CONCAT/JSON Idea as a solution 4 this
I'm trying to make sure the JSON string im sending back to my Flash project is ready to be properly parsed Invalid JSON parse input. keeps popping up..
so im thinking i need to properly have all the double quotes in the right places.
But in my MySQL query string, im trying to escape the double quotes, but then it makes my mySQL vars not work, for example...
If i do this..
GROUP_CONCAT('{\"ingredient\":', \"c.ingredient\", ',\"ingAmount\":', \"c.ingAmount\", '}')`
I get this...
{"ingredient":c.ingredient,"ingAmount":c.ingAmount},{"ingredient":c.ingredient,"ingAmount":c.ingAmount},{"ingredient":c.ingredient,"ingAmount":c.ingAmount}
How can i use all the double quotes to make the JSON properly formed without breaking the mysql?
This should do the trick:
SELECT food_ingredients.foodId
, food_ingredients.foodName
, food_ingredients.foodDescription
, food_ingredients.typeOfFood
, food_ingredients.ingredients
, AVG(food_ratings.food_rating) food_rating
, COUNT(food_ratings.foodId) number_of_votes
FROM (
SELECT a.foodId
, a.foodName
, a.foodDescription
, a.typeOfFood
, GROUP_CONCAT(
'{ingredient:', c.ingredient,
, ',ingAmount:', c.ingAmount, '}'
) ingredients
FROM foods a
LEFT JOIN foods_ing c
ON a.foodsId = c.foodsId
WHERE a.foodsId=4
GROUP BY a.foodId
) food_ingredients
LEFT JOIN food_ratings
ON food_ingredients.foodId = food_ratings.foodId
GROUP BY food_ingredients.foodId
Note that the type of query you want to do is not trivial in any SQL-based database.
The main problem is that you have one master (food) with two details (ingredients and ratings). Because those details are not related to each other (other than to the master) they form a cartesian product with each other (bound only by their relationship to the master).
The query above solves that by doing it in 2 steps: first, join to the first detail (ingredients) and aggregate the detail (using group_concat to make one single row of all related ingredient rows), then join that result to the second detail (ratings) and aggregate again.
In the example above, the ingredients are returned in a structured string, exactly like it appeared in your example. If you want to access the data inside PHP, you might consider adding a bit more syntax to make it a valid JSON string so you can decode it into an array using the php function json_decode(): http://www.php.net/manual/en/function.json-decode.php
To do that, simply change the line to:
CONCAT(
'['
, GROUP_CONCAT(
'{"ingredient":', c.ingredient
, ',"ingAmount":', c.ingAmount, '}'
)
, ']'
)
(this assumes ingredient and ingAmount are numeric; if they are strings, you should double quote them, and escape any double quotes that appear within the string values)
The concatenation of ingredients with GROUP_CONCAT can lead to problems if you keep a default setting for the group_concat_max_len server variable. A trivial way to mitigate that problem is to set it to the maximum theoretical size of any result:
SET group_concat_max_len = ##max_allowed_packet;
You can either execute this once after you open the connection to mysql, and it will then be in effect for the duration of that session. Alternatively, if you have the super privilege, you can change the value across the board for the entire MySQL instance:
SET GLOBAL group_concat_max_len = ##max_allowed_packet;
You can also add a line to your my.cnf or my.ini to set group_concat_max_lenght to some arbitrary large enough static value. See http://dev.mysql.com/doc/refman/5.5/en/server-system-variables.html#sysvar_group_concat_max_len
One obvious solution is to actually perform two queries:
1) get the food
SELECT a.foodId, a.foodName, a.foodDescription, a.typeOfFood
FROM `foods` a
WHERE a.foodsId=4
2) get all of its ingredients
SELECT c.ingredient, c.ingAmount
FROM `foods_ing` c
WHERE c.foodsId=4
This approach has the advantage that you don't duplicate data from the "foods" table into the result. The disadvantage is that you have to perform two queries. Actually you have to perform one extra query for each "food", so if you want to have a listing of foods with all their ingredients, you would have to do a query for each of the food record.
Other solutions usually have many disadvantages, one of them is using GROUP_CONCAT function, but it has a tough limit on the length of the returned string.
When you compare MySQL's aggregate functions and GROUP BY behavior to SQL standards, you have to conclude that they're simply broken. You can do what you want in a single query, but instead of joining directly to the table of ratings, you need to join on a query that returns the results of the aggregate functions. Something along these lines should work.
select a.foodId, a.foodName, a.foodDescription, a.typeOfFood,
c.ingredient, c.ingAmount,
b.numRatings, b.avgRating
from foods a
left join (select foodId, count(foodId) numRatings, avg(foodRating) avgRating
from foods_ratings
group by foodId) b on a.foodId = b.foodId
left join foods_ing c on a.foodId = c.foodId
order by a.foodId
I have a controller action that uses a sql query:
$tag = $this->params['tag'];
$this->set('projects', $this->Project->query('SELECT * FROM projects INNER JOIN projects_tags ON projects.id = projects_tags.project_id INNER JOIN tags on projects_tags.tag_id = tags.id WHERE tags.tag LIKE $tag'));
As you can see at the end I want to use a where clause with the $tag variable but I'm not sure how the syntax would go. As I'm getting the error
Unknown column '$tag' in 'where clause'
Can someone steer me in the right direction?
Ta,
Jonesy
I would strongly advise you to use the Cake ORM instead of raw queries, especially if you're going to plug URL parameters into it. Conditions on HABTM tables can be tricky, but you can build your joins using Cake's ORM syntax as well!
Read the manual, section 3.7.6.9 Joining tables.
Should you want to use Cake's ORM, the following code should provide results equivalent to your raw SQL query:
$this->loadModel('ProjectsTag'); // Load the joining table as pseudo-model
// Define temporary belongsTo relationships between the pseudo-model and the two real models
$this->ProjectsTag->bindModel(array(
'belongsTo' => array('Project','Tag')
));
// Retrieve all the join-table records with matching Tag.tag values
$result_set = $this->ProjectsTag->find('all',array(
'conditions' => array('Tag.tag LIKE' => "%{$tag}%")
));
// Extract the associated Project records from the result-set
$projects = Set::extract('/Project', $result_set);
// Make the set of Project records available to the view
$this->set(compact('projects'));
in php there's a difference between single and double quotes... basically, single quotes dont evaluate the variables... use double quotes instead
And i think that LIKE will need also single quotes.. i'm not really sure
"SELECT * FROM projects INNER JOIN projects_tags ON projects.id = projects_tags.project_id INNER JOIN tags on projects_tags.tag_id = tags.id WHERE tags.tag LIKE '$tag'"
i know.. i know.. people will start talkin' about sql injection.. and the need to scape the caracters... that's another question =)
good luck!
I would at least consider using the cakephp sanitize functions on your tag strings if they are user sourced. See http://book.cakephp.org/view/1183/Data-Sanitization or if using mysql as the db at least consider using http://www.php.net/manual/en/function.mysql-escape-string.php or do something to filter your user input. But the best thing is to make use of the CakePHP orm stuff.
Modify your query as:
$this->set('projects',
$this->Project->query("SELECT * FROM projects
INNER JOIN projects_tags
ON projects.id = projects_tags.project_id
INNER JOIN tags ON projects_tags.tag_id = tags.id
WHERE tags.tag LIKE '" . $tag . "'") //problem was here
);
and it will work.
In some languages (ColdFusion comes to mind), you can run a query on the result set from a previous query. Is it possible to do something like that in php (with MySQL as the database)?
I sort of want to do:
$rs1 = do_query( "SELECT * FROM animals WHERE type = 'fish'" );
$rs2 = do_query( "SELECT * FROM rs1 WHERE name = 'trout'" );
There is no MySQL function like this for PHP, however there is a more advanced substitute for it.
Edit: For those of you who don't know what a query of queries is, it's exactly this and there's a purpose some people do it like this. Using an AND operator is ****NOT**** the same thing! If I want results where username='animuson' for one part of my script and then want all the results out of that query where status='1', it is not logical for me to run another query using an AND operator, it is much more logical to loop through the previous results in PHP. Stop upvoting things without reading the comments on why they weren't upvoted in the first place, that's just lazy. If you don't have a clue what's being talked about, you shouldn't be upvoting or downvoting in the first place.
Well, you may want to do this without touching the db:
while($t = mysql_fetch_array($rs1)){
if($t[name] == 'trout'){
echo 'This is the one we\'re looking for!';
break;
}
}
In PHP, it would be terribly inefficient. You would have to loop through each row and check that its name was trout. However, is there any reason you can't do
SELECT * FROM `animals` WHERE `type` = 'fish' AND `name` = 'trout'
in SQL? It would be much, much faster.
You can also do something like
select morestuff from (select stuff from table where a = b ) where c = d;
Use the AND keyword?
"SELECT * FROM animals WHERE type = 'fish' and name='trout'"
Also, you can use LINQ for php http://phplinq.codeplex.com/