Mehmet Mutlu

ab -n 100 -c 10 http://www.yahoo.com/

ab -n 100 -c 10 http://127.0.0.1:8300/test.cfm > test1.txt &
ab -n 100 -c 10 http://127.0.0.1:8300/scribble.cfm > test2.txt &

Usage: ab [options] [http[s]://]hostname[:port]/path
Options are:
    -n requests     Number of requests to perform
    -c concurrency  Number of multiple requests to make
    -t timelimit    Seconds to max. wait for responses
    -b windowsize   Size of TCP send/receive buffer, in bytes
    -p postfile     File containing data to POST. Remember also to set -T
    -T content-type Content-type header for POSTing, eg.
        'application/x-www-form-urlencoded'
        Default is 'text/plain'
    -v verbosity    How much troubleshooting info to print
    -w              Print out results in HTML tables
    -i              Use HEAD instead of GET
    -x attributes   String to insert as table attributes
    -y attributes   String to insert as tr attributes
    -z attributes   String to insert as td or th attributes
    -C attribute    Add cookie, eg. 'Apache=1234. (repeatable)
    -H attribute    Add Arbitrary header line, eg. 'Accept-Encoding: gzip'
        Inserted after all normal header lines. (repeatable)
    -A attribute    Add Basic WWW Authentication, the attributes
        are a colon separated username and password.
    -P attribute    Add Basic Proxy Authentication, the attributes
        are a colon separated username and password.
    -X proxy:port   Proxyserver and port number to use
    -V              Print version number and exit
    -k              Use HTTP KeepAlive feature
    -d              Do not show percentiles served table.
    -S              Do not show confidence estimators and warnings.
    -g filename     Output collected data to gnuplot format file.
    -e filename     Output CSV file with percentages served
    -r              Don't exit on socket receive errors.
    -h              Display usage information (this message)
    -Z ciphersuite  Specify SSL/TLS cipher suite (See openssl ciphers)
    -f protocol     Specify SSL/TLS protocol (SSL2, SSL3, TLS1, or ALL)

“pivot table” or a “crosstab report”

(Note: this page needs to be wikified)

SQL Characteristic Functions: Do it without “if”, “case”, or “GROUP_CONCAT”. Yes, there is use for this…”if” statements sometimes cause problems when used in combination.

The simple secret, and it’s also why they work in almost all databases, is the following functions:

sign (x) returns -1,0, +1 for values x < 0, x = 0, x > 0 respectively
abs( sign( x) ) returns 0 if x = 0 else, 1 if x > 0 or x < 0
1-abs( sign( x) ) complement of the above, since this returns 1 only if x = 0

Quick example:   sign(-1) = -1,  abs( sign(-1) ) = 1,  1-abs( sign(-1) ) = 0

 CREATE TABLE exams (
        pkey int(11) NOT NULL auto_increment,
        name varchar(15),
        exam int,
        score int,
        PRIMARY KEY  (pkey)
      );

      insert into exams (name,exam,score) values ('Bob',1,75);
      insert into exams (name,exam,score) values ('Bob',2,77);
      insert into exams (name,exam,score) values ('Bob',3,78);
      insert into exams (name,exam,score) values ('Bob',4,80);

      insert into exams (name,exam,score) values ('Sue',1,90);
      insert into exams (name,exam,score) values ('Sue',2,97);
      insert into exams (name,exam,score) values ('Sue',3,98);
      insert into exams (name,exam,score) values ('Sue',4,99);

mysql> select * from exams;
+------+------+------+-------+
| pkey | name | exam | score |
+------+------+------+-------+
|    1 | Bob  |    1 |    75 |
|    2 | Bob  |    2 |    77 |
|    3 | Bob  |    3 |    78 |
|    4 | Bob  |    4 |    80 |
|    5 | Sue  |    1 |    90 |
|    6 | Sue  |    2 |    97 |
|    7 | Sue  |    3 |    98 |
|    8 | Sue  |    4 |    99 |
+------+------+------+-------+
8 rows in set (0.00 sec)

mysql> select name,
sum(score*(1-abs(sign(exam-1)))) as exam1,
sum(score*(1-abs(sign(exam-2)))) as exam2,
sum(score*(1-abs(sign(exam-3)))) as exam3,
sum(score*(1-abs(sign(exam-4)))) as exam4
from exams group by name;

+------+-------+-------+-------+-------+
| name | exam1 | exam2 | exam3 | exam4 |
+------+-------+-------+-------+-------+
| Bob  |    75 |    77 |    78 |    80 |
| Sue  |    90 |    97 |    98 |    99 |
+------+-------+-------+-------+-------+
2 rows in set (0.00 sec)

Note, the above pivot table was created with one select statement.

Let’s decompose to make the trick clearer, for the second exam:

mysql> select name, score, exam, exam-2, sign(exam-2), abs(sign(exam-2)), 1-abs(sign(exam-2)),
       score*(1-abs(sign(exam-2))) as exam2 from exams;
+------+-------+------+--------+--------------+-------------------+---------------------+-------+
| name | score | exam | exam-2 | sign(exam-2) | abs(sign(exam-2)) | 1-abs(sign(exam-2)) | exam2 |
+------+-------+------+--------+--------------+-------------------+---------------------+-------+
| Bob  |    75 |    1 |     -1 |           -1 |                 1 |                   0 |     0 |
| Bob  |    77 |    2 |      0 |            0 |                 0 |                   1 |    77 |
| Bob  |    78 |    3 |      1 |            1 |                 1 |                   0 |     0 |
| Bob  |    80 |    4 |      2 |            1 |                 1 |                   0 |     0 |
| Sue  |    90 |    1 |     -1 |           -1 |                 1 |                   0 |     0 |
| Sue  |    97 |    2 |      0 |            0 |                 0 |                   1 |    97 |
| Sue  |    98 |    3 |      1 |            1 |                 1 |                   0 |     0 |
| Sue  |    99 |    4 |      2 |            1 |                 1 |                   0 |     0 |
+------+-------+------+--------+--------------+-------------------+---------------------+-------+
8 rows in set (0.00 sec)

You may think IF’s would be clean but WATCH OUT! Look what the following gives (INCORRECT !!):

mysql> select name,
if(exam=1,score,null) as exam1,
if(exam=2,score,null) as exam2,
if(exam=3,score,null) as exam3,
if(exam=4,score,null) as exam4
from exams group by name;

+------+-------+-------+-------+-------+
| name | exam1 | exam2 | exam3 | exam4 |
+------+-------+-------+-------+-------+
| Bob  |    75 |  NULL |  NULL |  NULL |
| Sue  |    90 |  NULL |  NULL |  NULL |
+------+-------+-------+-------+-------+
2 rows in set (0.00 sec)

Note: the following does work – is all the maths necessary after all?

mysql> SELECT name,
       SUM(IF(exam=1,score,NULL)) AS exam1,
       SUM(IF(exam=2,score,NULL)) AS exam2,
       SUM(IF(exam=3,score,NULL)) AS exam3,
       SUM(IF(exam=4,score,0)) AS exam4
       FROM exams GROUP BY name;
+------+-------+-------+-------+-------+
| name | exam1 | exam2 | exam3 | exam4 |
+------+-------+-------+-------+-------+
| Bob  |    75 |    77 |    78 |    80 |
| Sue  |    90 |    97 |    98 |    99 |
+------+-------+-------+-------+-------+
2 rows in set (0.00 sec)

mysql> select name,
       sum(score*(1-abs(sign(exam-1)))) as exam1,
       sum(score*(1-abs(sign(exam-2)))) as exam2,
       sum(score*(1-abs(sign(exam-3)))) as exam3,
       sum(score*(1-abs(sign(exam-4)))) as exam4,
         sum(score*(1-abs(sign(exam- 2)))) -   sum(score*(1-abs(sign(exam- 1)))) as delta_1_2,
         sum(score*(1-abs(sign(exam- 3)))) -   sum(score*(1-abs(sign(exam- 2)))) as delta_2_3,
         sum(score*(1-abs(sign(exam- 4)))) -   sum(score*(1-abs(sign(exam- 3)))) as delta_3_4
       from exams group by name;
+------+-------+-------+-------+-------+-----------+-----------+-----------+
| name | exam1 | exam2 | exam3 | exam4 | delta_1_2 | delta_2_3 | delta_3_4 |
+------+-------+-------+-------+-------+-----------+-----------+-----------+
| Bob  |    75 |    77 |    78 |    80 |         2 |         1 |         2 |
| Sue  |    90 |    97 |    98 |    99 |         7 |         1 |         1 |
+------+-------+-------+-------+-------+-----------+-----------+-----------+
2 rows in set (0.00 sec)

Above delta_1_2 shows the difference between the first and second exams, with the numbers being positive because both Bob and Sue improved their score with each exam. Calculating the deltas here shows it’s possible to compare two rows, not columns which is easily done with the standard SQL statements but rows in the original table.

mysql>select name,
sum(score*(1-abs(sign(exam-1)))) as exam1,
sum(score*(1-abs(sign(exam-2)))) as exam2,
sum(score*(1-abs(sign(exam-3)))) as exam3,
sum(score*(1-abs(sign(exam-4)))) as exam4,
  sum(score*(1-abs(sign(exam- 2)))) -   sum(score*(1-abs(sign(exam- 1)))) as delta_1_2,
  sum(score*(1-abs(sign(exam- 3)))) -   sum(score*(1-abs(sign(exam- 2)))) as delta_2_3,
  sum(score*(1-abs(sign(exam- 4)))) -   sum(score*(1-abs(sign(exam- 3)))) as delta_3_4,

  sum(score*(1-abs(sign(exam- 2)))) -   sum(score*(1-abs(sign(exam- 1))))  +
  sum(score*(1-abs(sign(exam- 3)))) -   sum(score*(1-abs(sign(exam- 2))))  +
  sum(score*(1-abs(sign(exam- 4)))) -   sum(score*(1-abs(sign(exam- 3))))  as TotalIncPoints
  from exams group by name;

+------+-------+-------+-------+-------+-----------+-----------+-----------+----------------+
| name | exam1 | exam2 | exam3 | exam4 | delta_1_2 | delta_2_3 | delta_3_4 | TotalIncPoints |
+------+-------+-------+-------+-------+-----------+-----------+-----------+----------------+
| Bob  |    75 |    77 |    78 |    80 |         2 |         1 |         2 |              5 |
| Sue  |    90 |    97 |    98 |    99 |         7 |         1 |         1 |              9 |
+------+-------+-------+-------+-------+-----------+-----------+-----------+----------------+
2 rows in set (0.00 sec)

TotalIncPoints shows the sum of the deltas.

select name,
sum(score*(1-abs(sign(exam-1)))) as exam1,
sum(score*(1-abs(sign(exam-2)))) as exam2,
sum(score*(1-abs(sign(exam-3)))) as exam3,
sum(score*(1-abs(sign(exam-4)))) as exam4,
  sum(score*(1-abs(sign(exam- 2)))) -   sum(score*(1-abs(sign(exam- 1)))) as delta_1_2,
  sum(score*(1-abs(sign(exam- 3)))) -   sum(score*(1-abs(sign(exam- 2)))) as delta_2_3,
  sum(score*(1-abs(sign(exam- 4)))) -   sum(score*(1-abs(sign(exam- 3)))) as delta_3_4,

  sum(score*(1-abs(sign(exam- 2)))) -   sum(score*(1-abs(sign(exam- 1))))  +
  sum(score*(1-abs(sign(exam- 3)))) -   sum(score*(1-abs(sign(exam- 2))))  +
  sum(score*(1-abs(sign(exam- 4)))) -   sum(score*(1-abs(sign(exam- 3))))  as TotalIncPoints,

(sum(score*(1-abs(sign(exam-1)))) +
sum(score*(1-abs(sign(exam-2)))) +
sum(score*(1-abs(sign(exam-3)))) +
sum(score*(1-abs(sign(exam-4)))))/4 as AVG

from exams group by name;

+------+-------+-------+-------+-------+-----------+-----------+-----------+----------------+-------+
| name | exam1 | exam2 | exam3 | exam4 | delta_1_2 | delta_2_3 | delta_3_4 | TotalIncPoints | AVG   |
+------+-------+-------+-------+-------+-----------+-----------+-----------+----------------+-------+
| Bob  |    75 |    77 |    78 |    80 |         2 |         1 |         2 |              5 | 77.50 |
| Sue  |    90 |    97 |    98 |    99 |         7 |         1 |         1 |              9 | 96.00 |
+------+-------+-------+-------+-------+-----------+-----------+-----------+----------------+-------+
2 rows in set (0.00 sec)

It’s possible to combine Total Increasing Point TotalIncPoints with AVG. In fact, it’s possible to combine all of the example cuts of the data into one SQL statement, which provides additional options for displaying data on your page

select name,
sum(score*(1-abs(sign(exam-1)))) as exam1,
sum(score*(1-abs(sign(exam-2)))) as exam2,
sum(score*(1-abs(sign(exam-3)))) as exam3,
sum(score*(1-abs(sign(exam-4)))) as exam4,

(sum(score*(1-abs(sign(exam-1)))) +
sum(score*(1-abs(sign(exam-2)))))/2  as AVG1_2,

(sum(score*(1-abs(sign(exam-2)))) +
sum(score*(1-abs(sign(exam-3)))))/2 as AVG2_3,

(sum(score*(1-abs(sign(exam-3)))) +
sum(score*(1-abs(sign(exam-4)))))/2 as AVG3_4,

(sum(score*(1-abs(sign(exam-1)))) +
sum(score*(1-abs(sign(exam-2)))) +
sum(score*(1-abs(sign(exam-3)))) +
sum(score*(1-abs(sign(exam-4)))))/4 as AVG

from exams group by name;

+------+-------+-------+-------+-------+--------+--------+--------+-------+
| name | exam1 | exam2 | exam3 | exam4 | AVG1_2 | AVG2_3 | AVG3_4 | AVG   |
+------+-------+-------+-------+-------+--------+--------+--------+-------+
| Bob  |    75 |    77 |    78 |    80 |  76.00 |  77.50 |  79.00 | 77.50 |
| Sue  |    90 |    97 |    98 |    99 |  93.50 |  97.50 |  98.50 | 96.00 |
+------+-------+-------+-------+-------+--------+--------+--------+-------+
2 rows in set (0.00 sec)

Exam scores are listing along with moving averages…again it’s all with one select statement.

Good article on “Cross tabulations” or de-normalizing data to show stats: http://dev.mysql.com/tech-resources/articles/wizard/print_version.html

ADOdb (PHP) can generate pivot tables using PivotTableSQL().

For Perl, check DBIx-SQLCrosstab.

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