How to use defined variable in Where clause - oracle

Question

Defining and selecting variable works just fine in Oracle SQL Developer.
ALTER SESSION SET NLS_LANGUAGE=english; -- First day of week
--DEFINE SUMMER_START_DT = TO_CHAR(TO_DATE('03-24-2022', 'MM-DD-YYYY'),'yyyymmdd')
DEFINE SUMMER_START_DT = TO_CHAR(NEXT_DAY(LAST_DAY(TO_DATE(TO_CHAR('01/03/' || (EXTRACT(YEAR FROM SYSDATE)-1 + level) || '02:00:00'),'DD/MM/YYYY HH24:MI:SS')) - INTERVAL '7' DAY, 'SUNDAY'),'yyyymmdd') FROM DUAL CONNECT BY level <=1
SELECT &SUMMER_START_DT;
But I get an error when trying to use the variable in Select statement using it as filter in the Where clause.
SELECT a.* FROM TRADE a WHERE TO_CHAR(a.TRADE_DATE_TIME,'yyyymmdd') = &SUMMER_START_DT;
I get the error "SQL command not properly ended"
Hope someone can help me. Thanks
Kind regards
Soren Sig Mikkelsen

Answer 1

You substitution variable includes from dual, which is OK when you just prepend select in your first example; but in the second you end up with two from clauses:
SELECT a.*
FROM TRADE a
WHERE TO_CHAR(a.TRADE_DATE_TIME,'yyyymmdd') =
TO_CHAR(NEXT_DAY(LAST_DAY(TO_DATE(TO_CHAR('01/03/' || (EXTRACT(YEAR FROM SYSDATE)-1 + level) || '02:00:00'),'DD/MM/YYYY HH24:MI:SS')) - INTERVAL '7' DAY, 'SUNDAY'),'yyyymmdd')
FROM DUAL CONNECT BY level <=1
(You can see that in the generated column name/alias in the output grid; or set verify on and run as a script.)
If you really wanted to use that as the right-hand side of the filter then you could enclose it in parentheses:
SELECT a.* FROM TRADE a WHERE TO_CHAR(a.TRADE_DATE_TIME,'yyyymmdd') = (SELECT &SUMMER_START_DT);
which would become:
SELECT a.*
FROM TRADE a
WHERE TO_CHAR(a.TRADE_DATE_TIME,'yyyymmdd') =
(
SELECT TO_CHAR(NEXT_DAY(LAST_DAY(TO_DATE(TO_CHAR('01/03/' || (EXTRACT(YEAR FROM SYSDATE)-1 + level) || '02:00:00'),'DD/MM/YYYY HH24:MI:SS')) - INTERVAL '7' DAY, 'SUNDAY'),'yyyymmdd')
FROM DUAL CONNECT BY level <=1
)
But the connect by isn't doing anything here, so you can remove that; and if you remove from dual as well then you can run your first statement as:
SELECT &SUMMER_START_DT FROM DUAL;
and the second as it is.
You could simplify the calculation though. For a start you aren't using the time element, so you don't need to make it 2am; and you can truncate to the start of the year and add two months to get March 1st; as a string if that's really what you want:
to_char(next_day(last_day(add_months(trunc(sysdate, 'YYYY'), 2)) - 7, 'SUNDAY'), 'YYYYMMDD')
db<>fiddle
But you can keep it as a date; if you:
DEFINE SUMMER_START_DT = next_day(last_day(add_months(trunc(sysdate, 'YYYY'), 2)) - 7, 'SUNDAY')
then again you can do:
SELECT &SUMMER_START_DT FROM DUAL;
and your second query can be:
SELECT a.*
FROM TRADE a
WHERE a.TRADE_DATE_TIME >= &SUMMER_START_DT
AND a.TRADE_DATE_TIME < &SUMMER_START_DT + 1
which avoids converting every TRADE_DATE_TIME date value to a string to compare it, and allows an index on that date column to be used.