Tip

SQL: One SELECT for one or several row, same WHERE.

Some times we need a same "SELECT" to select several rows or a row from a table. With this we have to use two instructions, "SELECT" with different conditions of searching in "WHERE".

Example: We use a same "SELECT" instructions:

This SELECT, it obtains from table_1, all fields where fld_date = 2003 year and 01 month.
SELECT *
FROM table_1
WHERE fld_date = 200301

But, what happens when you need only an ID, for the same date (200301)? You can condition the WHERE instruction with... (to see code).

If you aux_ID variable it has some ID valid. You need that specific ID, or you need all IDs. 

   
  
SELECT fld_id, fld_name, fld_lastname, fld_date, .....
FROM   table_1
WHERE  fld_date = 200301 AND
       fld_id   = CASE
                  WHEN :aux_id > 0
                        THEN aux_id
                        ELSE fld_id
                  END

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This was first published in January 2003

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