title: Having subquery in each row in table is good or bad?
body: <p>I am having on case like multiple subquery in each mysql table. I donot know wheather this concept is good or bad when large size of database table. please suggest. here I have mysql function to run subquery in select statement itself.</p>
  
  <p>Here is mysql function GET_DEFAULT_VAL</p>
  
  <pre><code>DELIMITER $$
  CREATE DEFINER=`root`@`localhost` FUNCTION `GET_DEFAULT_VAL`(
    x text
  ) RETURNS text
  DETERMINISTIC
  BEGIN
    DECLARE columnList TEXT;
    SET group_concat_max_len = 65533;
    SELECT GROUP_CONCAT(`default_value` SEPARATOR ',')
    FROM `field_default_values` where find_in_set(`id`,x)
    INTO columnList;
    RETURN columnList;
  END$$
  </code></pre>
  
  <p>Here field_default_values table</p>
  
  <pre><code>------------------------------------
  id  |    multi_option_clm
  ------------------------------------
  
  1       option1
  
  2       option2
  
  3       option3
  
  4       option4 
  </code></pre>
  
  <p>Here is select statement</p>
  
  <pre><code>select id , multi_option_clm from table1;
  
  ------------------------------------
  id  |    multi_option_clm
  ------------------------------------
  
  1       1,2
  
  2       2,3,4
  
  
  
  select id, GET_DEFAULT_VAL(`multi_option_clm`) from table1;
  </code></pre>
  
  <p>I will show result as</p>
  
  <pre><code>------------------------------------
  id  |    multi_option_clm
  ------------------------------------
  
  1       option1,option2
  
  2       option2,option3,option4
  </code></pre>
  
  <p>will it cause any performance issue when large size database table ?</p>