Question

I have the below sql, which if i take out the inner join to the table and hard code the values, i get 2 records. But when i use the inner join statement, i just get 1 record. I am aware that with MYSQL, the like clause, is not case sensitive. Here is the sql below. I dont know why it is only returning row.

SELECT 
      a.project_code as projectCode, 
      a.project_name as projectName, 
      a.project_creation_date as projectCreationDate, 
      a.project_end_date as projectEndDate, 
      a.project_status as projectStatus      
from projects a 
inner join tmp_rec_naren8 b 
    on a.project_name like concat("%",b.expertise_desc,"%") 
    OR a.project_description like concat("%",b.expertise_desc,"%") ;

If I change the above to:

select *
from projects
where project_name like '%java%'
OR project_description like '%java%';

I get 2 rows and not 1.

Table tmp_rec_naren8 has just one column expertise_desc and contains this data:

expertise_desc
--------------
XML
Python
DWH
Java

Table projects has many columns :.. But these below are the relevant ones

    project_code sr_user_name project_name project_descriiption ..
    -----------------------------------------------------------
    1             naren5      POS          C++, XML,Java
    2             naren7      INV          Networking
    3             naren9      CCV          Java, Unix         

The first query returns 1 row:

    project_code sr_user_name project_name project_descriiption ..
    ---------------------------------------------------------------
     1            naren5       POS         C++,XML,Java

The second query returns 2 rows

    project_code sr_user_name project_name project_descriiption ..
    -----------------------------------------------------------
    1             naren5      POS          C++, XML,Java
    3             naren9      CCV          Java, Unix         

Answer 1

One explanation would be if the value in expertise_desc contained a trailing space, ie 'Java ' (not 'Java'). Then the concat value would be '%java %', not '%java%', making a difference.

If one of your project names ended with java, and the other had java within the name, only one would match using the join, but two would match with the non-join.