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.
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