CASE WHEN EXISTS in WHERE clause

I want to print all employee names and also if the employee is present in a table.


|  EMP_ID  | ENAME    |
| -------- | -------- |
|  1       |  ALLEN   |
|  2       |  MAX     |
|  3       |  BEN     |


|  EMP_ID  | EC_CODE   |
| -------- | --------  |
|  1       |  CONFIG_1 |
|  2       |  CONFIG_2 |
|  3       |  CONFIG_1 |



SELECT ename, 
            (CASE WHEN EXISTS (SELECT 1 FROM m_sys.m_emp_config ec WHERE ec_code = 'CONFIG_1' AND emp_id = emp.emp_id) THEN
              'Y' 
             ELSE 
              'N' 
             END ) config
        FROM emp emp

Can we write the CASE WHEN EXISTS in the Where clause instead of there?

I am new with SQL, please help me?

Expected Output for the sql:

>Solution :

Your current query is correct for doing this via exists. Here is an alternative version using a left join:

SELECT DISTINCT
    e.ENAME,
    CASE WHEN ec.EMP_ID IS NOT NULL THEN 'Y' ELSE 'N' END AS CONFIG
FROM emp e
LEFT JOIN m_sys.m_emp_config ec
    ON ec.EMP_ID = e.EMP_ID AND
       ec.ec_code = 'CONFIG_1'
ORDER BY e.EMP_ID;