I'm currently learning how to build a site in PHP MySQL. However, I seem to fail to understand COUNT() as count and wouldn't mind some further explanation.
I get the principles of COUNT, 0 || 1, and how it returns all the values that pertain to that query.
But, don't see how COUNT as count works. Anyhow, this is how the code I'm writing goes - so we have a working example - and where I first became perplexed.
"SELECT COUNT(id) as count, id
FROM user
WHERE email='$email' AND password='".md5$password."'"
That is what is called alias which is sometimes used to show a more appealing column header to users or the calling code
SELECT COUNT(`id`) as `count`....
will print
count
--------
5
The alias standing as the column header instead of any arbitrary string: See the SQLFiddle to see the difference
From the fiddle you can see that the header column looks somehow e.g.
count(*)
--------
5
With Count() you can count the returning rows of a result set. The also the official MySQL documentation about count:
Databases are often used to answer the question, “How often does a certain type of data occur in a table?” For example, you might want to know how many pets you have, or how many pets each owner has, or you might want to perform various kinds of census operations on your animals.
Counting the total number of animals you have is the same question as “How many rows are in the pet table?” because there is one record per pet. COUNT(*) counts the number of rows, so the query to count your animals looks like this:
SELECT COUNT(*) FROM pet;
The part with AS count means that this colum will get a name which you can use e.g. in PHP. See also this explenation on w3schools:
You can give a table or a column another name by using an alias. This can be a good thing to do if you have very long or complex table names or column names.
An alias name could be anything, but usually it is short.
as count is just an alias. You can use as for any field or method selected. it means you change the name of the column being returned in your dataset.
SELECT `field` as another_name
So:
SELECT COUNT(*) as `count`
Just renames the column from COUNT(*) to count making it easier to work with whereever you are maniuplating your result set.
It also makes for easier access within your current query. Many would do the following with large table names:
SELECT * FROM `table_with_ridiculous_name` as twrn WHERE twrn.id = 1
If you ran this sql:
SELECT COUNT(id), id ....
You would get (after doing a *_fetch_assoc) $row['numberofrecordshere'] which would be very hard to echo (or use in a comparison) unless you knew how many records there would be (which would defeat the purpose of this result, anyway)
Returning it as count allows you to get to it in the resulting array by using $row['count']
Related
Using PHP a secure user will enter a Ref (ex. NB093019) a query will be used to determine which PO(s) have that Ref and if they have any quantity. The issue is that we have 86 columns to check if that Ref is in and then once it finds what column it is in how to check the corresponding column that contains that quantity( the table cannot be edited).
I can make this work with 86 if else statements in PHP and then more if else statements inside of each PHP statement. I have no launching point once i do the initial query.
select 'remainder'as prefix, po, *comments,*GuideRef, *Qty
from remainder
where ('NB092419')IN (NWANTcomments,NWANTGuideRef,NWANTpreviouscomments,
NWANTpreviousGuideRef,NWANTprevious2comments,
NWANTprevious2GuideRef, BPrev2GuideRef,
BPrev2comments, BPrevGuideRef, BPrevcomments,
aGuideRef, Mcomments,MGuideRef,acomments,
MAGuideRef,BOGuideRef )
group by po
I have removed some of the in() information so it is not so long also the *comments, *GuideRef, *Qty would be decided by which one of the columns in the IN() statement returns information. Is this even possible
You could perhaps write an SQL that writes an SQL:
select REPLACE(
'SELECT ''{colstub}GuideRef'' as which, {colstub}Qty FROM remainder WHERE {colstub}Ref like ''%somevalue%'' UNION ALL',
'{colstub}',
REPLACE(column_name, 'GuideRef', '')
)
FROM information_schema.columns
WHERE table_name = 'remainder' and column_name LIKE '%Ref'
It works like "pull all the column names out of the info schema where the column name is like %guideref, replace guideref with nothing to get just the fragment of the column name that is varied: NWANTguideref -> NWANT, NWANTpreviousguideref -> NWANTprevious ... then uses this stub to form a query that gives a string depicting the column name, the qty from the quantity column, where the relevant guideref column is LIKE some value"
If you run this it will produce a result set like:
SELECT 'aGuideRef' as which, aQty FROM table WHERE aGuideRef LIKE '%lookingfor%' UNION ALL
SELECT 'bGuideRef' as which, bQty FROM table WHERE bGuideRef LIKE '%lookingfor% ...
So it's basically utputted a load of strings that are SQLs in themselves. It might need a bit of fine tuning, and hopefully all your columns are reliably and rigidly like xQty, xGuideRef, xComments triplets, but it essentially writes most the query for you
If you then copy the result set out of the results grid and paste it back into the query window, remove the last UNION ALL and run it, it will search the columns and tell you where it was found as well as the quantity
It's not too usable for a production system, but you could do the same in php- run the query, get the strings into another sql command, re-run it..
I would suggest you consider changing your table structure though:
prefix, qty, guideref, comments
You shouldn't have 86 columns that are the mostly same thing; you should have one column that is one of 86/3 different values then you can just query the guideref and the type. If this were an address table, I'm saying you **shouldn't* have HomeZipcode, WorkZipcode, UniversityZipcode, MomZipcode, DadZipcode.. and every time you want to store another kind of address you add more columns (BoyfriendZipcode, GirlfriendZipcode, Child1Zipcode...). Instead if you just had an "addresstype" column then you can store any number of different kinds of addresses without recompiling your app and changing your db schema
You can use this technique to re-shape the table - write an SQL that writes a bunch of UNION ALL sqls (without WHERE clauses), one of the columns should be the "recordtype" column (from colstub) and the other columns should just be "qty", "guide", "comments". Once you have your result set with the unions you can make a table to hold these 4 things, and then place INSERT INTO newtable at the head of the block of unions
Am using a SQL command in PHP to count the no of values inserted in a column named attack_type. I want to count the occurrence of individual values like website defacement in the whole column of the table. But here the column attack_type contain different values, separated by a comma and the count is treating whole column data as a string. Below is my current SQL statement with its output
I tried explode print_r in PHP
SELECT attack_type,
count(*) as number
FROM data_input_test
GROUP BY attack_type
Here is the output of the above statement
generated:
https://drive.google.com/open?id=1TyRL_Mh0OOJWaCpFczxmBr34No9LUpzH
But what I want is :
https://drive.google.com/open?id=1eeA_1TCER0WMpZwSkBDMzRtRa8xihbZd
and so on. The above desired output is edited to show what I exactly want.
Other answer on stackoverflow and on other forums are either irrelevant or are using regrex or a new table creation in one or the other way. That I don't want as my hosting has some limitations. My hosting doesnt provide creation of triggers, regrex or creation of temp tables
I may have a solution for this but don't know how to apply here. Possible here: https://www.periscopedata.com/blog/splitting-comma-separated-values-in-mysql
Please someone explain me how to apply the same here.
So I finally worked around to get my work done using the select only. This only works if you have a finite set of data or specifically less than 64 values.
Change your column datatype to 'set' type. And enter your set values.
Now use select, count, find_in_set and union functions of sql.
Example:
union select 'Un-patched Vulnerable Software Exploitaion'as type, count(*) as number from data_input_test where find_in_set('Un-patched Vulnerable Software Exploitaion',attack_type)```
and so on for all your values
I know this is not how you should do but as the legends say this works 😎😎
If you just want to count comma-separated values in rows, you can use:
SELECT SUM(LENGTH(attack_type) - LENGTH(replace(attack_type, ',', '')) +1) AS TotalCount
FROM table_name;
I'm not very experienced with more advanced MySQL query stuff.. (mostly basic queries, return and parse response..etc)
However.. I am not clear on the correct approach when I need multiple things (responses) from the database.. Is there a way to get these things from the single query? or do I need to do a new query for each time?
Background:
I use PDO to do a SELECT statement
ie:
$getAllVideos_sql = "SELECT * as FROM $tableName WHERE active IS NOT NULL OR active != 'no' ORDER BY topic, speaker_last, title;";
$getAllVideos_stmt = $conn->prepare($getAllVideos_sql);
$getAllVideos_stmt->execute();
$getAllVideos_stmt->setFetchMode(PDO::FETCH_ASSOC);
$results = $getAllVideos_stmt->fetch(PDO::FETCH_ASSOC);
//parse as I see fit
This gives me my 'chunk of data' that I can pick apart and display as I want.
However.. I want to also be able to give some stats (totals)
For the total (distinct) 'topics'.. as well as total count for the 'titles' (should all be unique by default)
Do I need to do another query, prepare, execute, setFetchMode, fetch all over again?
Is this the proper way to do this? Or is there a way to crib off the initial commands that are already in play?
To be clear, I'm not really looking for a query... I'm looking to understand the proper way one does this.. when they need several pieces of data like I do? multiple queries and executions..etc?
Or maybe it can and -should- be done in one snippet? With an adjustment to the query itself to return sub select/queries info?
this isnt the correct syntax, because it only returns 1 record..(but the total topic count seems to be correct, even though I only get 1 record returned)
SELECT *, count(DISTINCT topic)as totalTopics, count(DISTINCT title)as totalTitles FROM $tableName;
Maybe this the more proper approach? Try to include these totals/details in the main query to pick out?
Hope this makes sense.
Thanks
I don't think you're going to get anything very clean that'll do this, however something like this might work:
SELECT * from $Table t
INNER JOIN (
SELECT COUNT(DISTINCT Topic) as TotalTopics FROM $Table
) s ON 1 = 1
INNER JOIN (
SELECT COUNT(DISTINCT Title) as TotalTitles FROM $Table
) f ON 1 = 1
WHERE ( Active IS NOT NULL ) AND Active != 'no'
Especially with web applications, many people are regularly doing counts or other aggregations somewhere along the way. Sometimes if it is a global context such as all topics for all users, having some stored aggregates helps rather than requerying all record counts every time.
Example. If you have a table with a list of "topics", have a column in there for uniqueTitleCount. Then, based on a trigger, when a new title is added to a topic, the count is automatically updated by adding 1. You can pre-populate this column by doing a correlated update to said "topics" table, then once the trigger is set, you can just have that column.
This also works as I see many times that people want "the most recent". If your system has auto-increment IDs in the tables, similarly, have the most recent ID created for a given topic, or even most recent for a given title/document/thread so you don't have to keep doing something like.
select documentID, other_stuff
from sometable
where documentID in ( select max( documentID )
from sometable
where the title = 'something' )
Use where these make sense then your optimization pull-downs get easier to handle. You could even have a counter per document "title" and even a most recent posting date so they can quickly be sorted based on interest, frequency of activity, whatever.
I have a MySQL database that contains over 400,000 rows. For my web based script, I have a page function. One of the steps to determine how many pages there should be is returning the number of rows in the table.
Let's pretend the table name is data.
I'm wondering what is the most efficient method to ONLY return the number of rows in the database.
I could obviously do something like:
$getRows = mysql_query("SELECT id FROM `data`") or die(mysql_error());
$rows = mysql_num_rows($getRows);
So that it only selects the id. But still, that will be selecting 400,000 + ID's worth of data and storing it on the stack (i think?) and seems less efficient as using a method such as finding the table status. I'm just not 100% sure how to use the table status method.
Feedback & opinions would be awesome. Thanks guys!
use count
SELECT count(id) FROM data
See this question for more info on getting counts. Make sure your id has an index in your table.
Now, to find the number of unique rows, you can do
SELECT count(distinct(id)) FROM data
alternatively, if you want to find the highest ID number (if you ID are autoincremental and unique) you can try SELECT max(id) FROM data to return the highest ID number present.
I'd highly recommend this site to learn these basic functions:
http://sqlzoo.net/
400,000 rows is not a lot at all. Keep it simple and just do:
select count(*)
from `data`
I have a table in MySQL that I'm accessing from PHP. For example, let's have a table named THINGS:
things.ID - int primary key
things.name - varchar
things.owner_ID - int for joining with another table
My select statement to get what I need might look like:
SELECT * FROM things WHERE owner_ID = 99;
Pretty straightforward. Now, I'd like users to be able to specify a completely arbitrary order for the items returned from this query. The list will be displayed, they can then click an "up" or "down" button next to a row and have it moved up or down the list, or possibly a drag-and-drop operation to move it to anywhere else. I'd like this order to be saved in the database (same or other table). The custom order would be unique for the set of rows for each owner_ID.
I've searched for ways to provide this ordering without luck. I've thought of a few ways to implement this, but help me fill in the final option:
Add an INT column and set it's value to whatever I need to get rows
returned in my order. This presents the problem of scanning
row-by-row to find the insertion point, and possibly needing to
update the preceding/following rows sort column.
Having a "next" and "previous" column, implementing a linked list.
Once I find my place, I'll just have to update max 2 rows to insert
the row. But this requires scanning for the location from row #1.
Some SQL/relational DB trick I'm unaware of...
I'm looking for an answer to #3 because it may be out there, who knows. Plus, I'd like to offload as much as I can on the database.
From what I've read you need a new table containing the ordering of each user, say it's called *user_orderings*.
This table should contain the user ID, the position of the thing and the ID of the thing. The (user_id, thing_id) should be the PK. This way you need to update this table every time but you can get the things for a user in the order he/she wants using ORDER BY on the user_orderings table and joining it with the things table. It should work.
The simplest expression of an ordered list is: 3,1,2,4. We can store this as a string in the parent table; so if our table is photos with the foreign key profile_id, we'd place our photo order in profiles.photo_order. We can then consider this field in our order by clause by utilizing the find_in_set() function. This requires either two queries or a join. I use two queries but the join is more interesting, so here it is:
select photos.photo_id, photos.caption
from photos
join profiles on profiles.profile_id = photos.profile_id
where photos.profile_id = 1
order by find_in_set(photos.photo_id, profiles.photo_order);
Note that you would probably not want to use find_in_set() in a where clause due to performance implications, but in an order by clause, there are few enough results to make this fast.