Home/ Questions/Q 7973167
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-04T08:02:15+00:00

I have recently written a survey application that has done it’s job and all

  • 0

I have recently written a survey application that has done it’s job and all the data is gathered. Now i have to analyze the data and i’m having some time issues.
I have to find out how many people selected what option and display it all.

I’m using this query, which does do it’s job:

SELECT COUNT(*)
  FROM survey
 WHERE users = ? AND table = ? AND col = ? AND row = ? AND selected = ?
 GROUP BY users,table,col,row,selected

As evident by the “?” i’m using MySQLi (in php) to fetch the data when needed, but i fear this is causing it to be so slow.

The table consists of all the elements above (+ an unique ID) and all of them are integers.
To explain some of the fields:
Each survey was divided into 3 or 4 tables (sized from 2×3 to 5×5) with a 1 to 10 happiness grade to select form. (questions are on the right and top of the table, then you answer where the questions intersect)

users – age groups

table, row, col – explained above

selected – dooooh explained above

Now with the surveys complete and around 1 million entries in the table the query is getting very slow. Sometimes it takes like 3 minutes, sometimes (i guess) the time limit expires and you get no data at all. I also don’t have access to the full database, just my empty “testing” one since the costumer is kinda paranoid :S (and his server seems to be a bit slow)

Now (after the initial essay) my questions are: I left indexing out intentionally because with a lot of data being written during the survey, it would be a bad idea. But since no new data is coming in at this point, would it make sense to index all the fields of a table? How much sense does it make to index integers that never go above 10? (as you can guess i haven’t got a clue about indexes). Do i need the primary unique ID in this table? I

I read somewhere that indexing may help groups but only if you group by the first columns in a table (and since my ID is first and from my point of view useless can i remove it and gain anything by it?)

Is there another way to write my query that would basically do the same thing but in a shorter period of time?

Thanks for all your suggestions in advance!

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Add an index on entries that you “GROUP BY” or do “WHERE”. So that’s ONE index incorporating users,table,col,row and selected in your case.

    Some quick rules:

    • combine fields to have the WHERE first, and the GROUP BY elements last.
    • If you have other queries that only use part of it (e.g. users,table,col and selected) then leave the missing value (row, in this example) last.

    Don’t use too many indexes/indeces, as each will slow the table to updates marginally – so on really large system you need to balance queries with indexes.

    Edit: do you need the GROUP BY user,col,row as these are used in the WHERE. If the WHERE has already filtered them out, you only need group by “selected”.

    • 0