More complicated data profiling query

This is the extended version of basic-data-profiling, it is slower but gives you much more interesting informations.

When you do data profiling you need to give examples for each data grouping, GROUP_CONCAT MySQL function is here for you

SELECT COUNT(*) AS nb, tablename.title AS datas, 
 SUBSTRING_INDEX(GROUP_CONCAT(tablename.emp_no ORDER BY RAND(42)), ',', 10) AS Examples
FROM titles AS tablename
GROUP BY datas
ORDER BY nb DESC;

Result:

nb	datas	Examples
115003	Engineer	222309,64167,287849,222887,256836,237309,262823,242428,222680,225055
107391	Staff	427715,209965,36589,74250,407627,251530,409579,254748,456807,204250
97750	Senior Engineer	238256,468681,477369,205608,224208,263874,251767,82661,245168,213359
92853	Senior Staff	83208,45313,211968,264723,36232,263944,46428,471920,66956,442742
15159	Technique Leader	260169,436055,295995,251618,434080,492772,54096,18718,97636,496663
15128	Assistant Engineer	448269,461300,443947,417358,21784,437352,412830,94900,262281,98231
24	Manager	110511,110800,110022,110303,111133,110420,110567,110854,111784,111692

Explainations:
COUNT(*) will count the number of records for each value grouped in the GROUP BY clause

tablename.title AS datas will show in the column "datas" the name of the current group 

GROUP_CONCAT will join the string value of the first arg with coma between them, the max size of group_concat is set by group_concat_max_len variable, default is 1024chars

ORDER BY RAND(42) is the internal order of the group_concat, in this case we order by random with the seed 42, if you rerun the query you will have exactly the same random order if you use the same seed. If you want different examples each time just change the seed or use ORDER BY RAND() instead
SUBSTRING_INDEX is looking for the comma separator and will keep only  everything left of the 10th comma
ORDER by nb DESC will order the final result by the number of occurrence of each data putting the most use data top of the table