在Where子句SQL中使用Case

Question

Hi to make this short.

I need only the column when a condition is met. if the condition is not met, then I can proceed running my Query without that column as validation.

CONDITION NEEDED.

REFERENCE TABLE - TABLE_A
inside TABLE_A there is PARAMETER_NAME AND PARAMETER_VALUE
REQUIRED: PARAMETER_NAME= 'SMS_SEND'
PARAMETER_VALUE = 'TRUE'

COLUMN FOR VALIDATION INSIDE TABLE_B INVALID_STAT ---> COLUMN

IF PARAMETER_NAME= 'SMS_SEND' and PARAMETER_VALUE = 'TRUE'
THEN I NEED TO CHECK INVALID_STAT IF ITS EQUAL TO 'Y'
ELSE
I DONT NEED TO VALIDATE INVALID_STAT AT ALL



WHERE (CASE
           WHEN 1 = (SELECT DECODE (PARAMETER_VALUE, 'FALSE', 1, 2)
                       FROM TABLE_A
                      WHERE PARAMETER_NAME = 'SMS_SEND')
           THEN
              INVALID_STAT
           ELSE
              'Y'
        END) = 'Y'

Answer 1

based upon your commentary, this will get you what you have asked for.

However, I doubt this is what you need. Please update your question as requested in the commentary above. If this does answer your question, please accept it as the answer and close the question.

I expect that the real requirement will be to wrap the following query in an outer join to a larger query (which you have not supplied) along with a coalesce to deal with the possible no rows scenario.

select 
  case
    when PARAMETER_VALUE = 'FALSE' THEN 'Y'
    else ''
  end as SMS_Send_Ind
from Table_A
where PARAMETER_Name = 'SMS_SEND'
;

If there is no record in the table with Parameter_name = 'SMS_SEND', then the query will return no rows. Otherwise it will a Y or a blank as determined by the number of records in Table_A with parameter_name = 'SMS_SEND'