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Editorial Team
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Asked: 2026-05-18T02:05:32+00:00

When trying to execute this query my mysql server cpu usage goes to 100%

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When trying to execute this query my mysql server cpu usage goes to 100% and the page just stalls. I setup an index on (Client_Code, Date_Time, Time_Stamp, Activity_Code, Employee_Name, ID_Transaction) it doesn’t seem to help. Now I need different way to make this query so its not so taxing on the server. Below is a description of what I need it to do. To explain it looks for the last entry under each client code for the specfic day then once it has found them all. It then counts how many of these entries Eric or Jerry has for example. Ill need to see code I’m not to familiar yet. Thank you for you help.

Here is what this query does

Database info 

ID_Transaction | Client_Code | Employee_Name | Date_Time |Time_Stamp| Activity_Code  
1              | 00001       |  Eric         |  11/15/10 | 7:30AM   |  00023  
2              | 00001       |  Jerry        |  11/15/10 | 8:30AM   |  00033  
3              | 00002       |  Amy          |  11/15/10 | 9:45AM   |  00034  
4              | 00003       |  Jim          |  11/15/10 | 10:30AM  |  00063  
5              | 00003       |  Ryan         |  11/15/10 | 12:00PM  |  00063  
6              | 00003       |  bill         |  11/14/10 | 1:00pm   |  00054    
7              | 00004       |  Jim          |  11/15/10 | 1:00pm   |  00045  
8              | 00005       |  Jim          |  11/15/10 | 10:00 AM |  00045

The query takes the info above and counts it like so. By the most recent entry for each client_code. In this case the query would look like this. After php. 

Jerry = 1    
2               | 00001       |  Jerry        |   11/15/10 |   8:30AM |   00033     
Amy = 1   
3               | 00002       |  Amy          |   11/15/10 |   9:45AM |  00034   
Ryan = 1  
5               | 00003       | Ryan          |   11/15/10 |   12:00PM | 00063  
Jim = 2  
7               | 00004       | Jim           |   11/15/10 |   1:00pm  | 00045  
8               | 00005       | Jim           |   11/15/10 |   10:00 AM| 00045

And the query:

 SELECT m.Employee_Name, count(m.ID_Transaction)   
     FROM ( 
         SELECT DISTINCT Client_Code 
             FROM Transaction
         ) md 
         JOIN Transaction m ON 
             m.ID_Transaction = ( 
                 SELECT ID_Transaction 
                     FROM Transaction mi  
                     WHERE mi.Client_Code = md.Client_Code 
                         AND Date_Time=CURdate() 
                         AND Time_Stamp!='' 
                         AND Activity_Code!='000001'  
                     ORDER BY m.Employee_Name DESC, 
                         mi.Client_Code  DESC, 
                         mi.Date_Time DESC,  
                         mi.ID_Transaction DESC 
                     LIMIT 1 
             )   
         GROUP BY m.Employee_Name    



+----+--------------------+-------------+--------+------------------------+--------------+---------+----------------+--------+----------------------------------------------+
| id | select_type        | table       | type   | possible_keys          | key          | key_len | ref            | rows   | Extra                                        |
+----+--------------------+-------------+--------+------------------------+--------------+---------+----------------+--------+----------------------------------------------+
|  1 | PRIMARY            | <derived2>  | ALL    | [NULL]                 | [NULL]       | [NULL]  | [NULL]         |    347 | Using temporary; Using filesort              |
|  1 | PRIMARY            | m           | index  | [NULL]                 | search index | 924     | [NULL]         |  29255 | Using where; Using index; Using join buffer  |
|  3 | DEPENDENT SUBQUERY | mi          | ref    | search index,secondary | search index | 18      | md.Client_Code |   2926 | Using where; Using temporary; Using filesort |
|  2 | DERIVED            | Transaction | range  | [NULL]                 | search index | 18      | [NULL]         |     10 | Using index for group-by                     |
+----+--------------------+-------------+--------+------------------------+--------------+---------+----------------+--------+----------------------------------------------+
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1 Answer

  1. Editorial Team

    You should try running

    EXPLAIN SELECT m.Employee_Name, count(m.ID_Transaction)   
FROM ( SELECT DISTINCT Client_Code FROM Transaction) md 
JOIN Transaction m
  ON m.ID_Transaction = ( SELECT ID_Transaction FROM Transaction mi  
                          WHERE mi.Client_Code = md.Client_Code AND
                                Date_Time=CURdate() AND 
                                Time_Stamp!='' AND 
                                Activity_Code!='000001'  
                          ORDER BY m.Employee_Name DESC,
                                   mi.Client_Code  DESC, 
                                   mi.Date_Time DESC,
                                   mi.ID_Transaction DESC LIMIT 1 
                        )  
GROUP BY m.Employee_Name

    to get an indication of how the query optimizer is processing your query.

    I do notice that you’re hitting the same table 3 times. I’m guessing that’s causing the optimizer some challenges.

    It might make more sense to just write a simpler SQL query and then use PHP to pare it down to what you’re looking for.

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