SQL Where-Clause with Case Statement sort date - sql

Question

I have a problem again and can't ask anyone at the moment. I want to include a switch-case in a SQL SELECT which filters by date.
The goal is to display a simple grid in a window and filter my data by a date "where".
On the one hand I want to search for everything that exists in the year = e.g. '2022'.
Then I want to search only for calendar weeks = e.g. '23'.
Then show me only the month = eg. '07'
and just the complete date = e.g. '22.07.2022'.
SELECT
ID
, GEN_DATUM
FROM
TABLE_XY
WHERE
CASE
WHEN '{DATUM_MODUS}' = '#JA' THEN TO_CHAR(GEN_DATUM, 'yyyy') = TO_CHAR('{DATUM}' , 'yyyy')
WHEN '{DATUM_MODUS}' = '#KW' THEN TO_CHAR(GEN_DATUM, 'IW') = TO_CHAR('{DATUM}' , 'IW')
WHEN '{DATUM_MODUS}' = '#MO' THEN TO_CHAR(GEN_DATUM, 'MM') = TO_CHAR('{DATUM}' , 'MM')
WHEN '{DATUM_MODUS}' = '#WO' THEN TO_CHAR(GEN_DATUM, 'DD.MM.YYYY') = TO_CHAR('{DATUM}' , 'MM')
ELSE NULL
END
In the source code I pass parameters that I need for further processing. Here I want to say
if I want to search for year 'DATUM_MODUS' = #JA then show me the year
System.Collections.Hashtable htPARAM = new System.Collections.Hashtable()
{
["DATUM"] = Datum,
["DATUM_MODUS"] = Datum_MODUS,
};

Answer 1

Use AND and OR rather than a CASE expression.
Never build an SQL statement using string concatenation or template strings as you introduce SQL injection vulnerabilities; use bind variables instead.
If you use functions on the gen_datum column then Oracle will not be able to use an index on that column (and would require function-based indexes instead). Instead, change the datum value into a date and match the start and end of each date range and then Oracle can use an index on the gen_datum column.
Like this:
SELECT ID
, GEN_DATUM
FROM TABLE_XY
WHERE ( :datum_modus = '#JA'
-- Search by year
AND gen_datum >= TO_DATE(:datum || '-01-01', 'YYYY-MM-DD')
AND gen_datum < TO_DATE((:datum + 1) || '-01-01', 'YYYY-MM-DD')
)
OR ( :datum_modus = '#KW'
-- Search by ISO week in the current year
AND gen_datum >= TRUNC(TRUNC(SYSDATE, 'YY') + 3, 'IW') + 7 * (:datum - 1)
AND gen_datum < TRUNC(TRUNC(SYSDATE, 'YY') + 3, 'IW') + 7 * :datum
)
OR ( :datum_modus = '#MO'
-- Search by month in the current year
AND gen_datum >= ADD_MONTHS(TRUNC(SYSDATE, 'YY'), :datum - 1)
AND gen_datum < ADD_MONTHS(TRUNC(SYSDATE, 'YY'), :datum)
)
OR ( :datum_modus = '#WO'
-- Search by date
AND gen_datum >= TO_DATE(:datum, 'DD.MM.YYYY')
AND gen_datum < TO_DATE(:datum, 'DD.MM.YYYY') + 1
)

Answer 2

The with clause is here just to generate some sample data and, as such, it is not a part of the answer.
You missunderstood the CASE expression. CASE expression returns a value and you are trying to get another expression out of it. Also you have to keep in mind
that CASE is tested sequentially meaning that the first one with WHEN condition satisfied will return the THEN part and EXIT CASE.
Having that in mind all you have to do is compare two CASE expresions (two returned values) and try to get the result. WHEN clauses in both of them should be rearrenged too.
Try something like this:
WITH
tbl AS
(
SELECT 1 "ID", To_Date('08.01.2022', 'dd.mm.yyyy') "GEN_DATUM" FROM DUAL UNION ALL
SELECT 2 "ID", To_Date('23.04.2022', 'dd.mm.yyyy') FROM DUAL UNION ALL
SELECT 3 "ID", To_Date('17.06.2022', 'dd.mm.yyyy') FROM DUAL UNION ALL
SELECT 4 "ID", To_Date('19.06.2022', 'dd.mm.yyyy') FROM DUAL
)
SELECT
ID,
TO_CHAR(GEN_DATUM, 'dd.mm.yyyy') "GEN_DATUM",
TO_CHAR(GEN_DATUM, 'iw') "WEEK_OF_GEN_DATUM",
TO_CHAR(GEN_DATUM, 'mm') "MONTH_OF_GEN_DATUM",
TO_CHAR(GEN_DATUM, 'yyyy') "YEAR_OF_GEN_DATUM",
:DATUM_MODUS "DATUM_MODUS",
TO_CHAR(:DATUM, 'dd.mm.yyyy') "DATUM"
FROM
tbl
WHERE
CASE
WHEN :DATUM_MODUS = '#WO' THEN TO_CHAR(GEN_DATUM, 'dd.mm.yyyy') -- the most distinctive (365)
WHEN :DATUM_MODUS = '#KW' THEN TO_CHAR(GEN_DATUM, 'iw') -- second (52)
WHEN :DATUM_MODUS = '#MO' THEN TO_CHAR(GEN_DATUM, 'mm') -- next (12)
WHEN :DATUM_MODUS = '#JA' THEN TO_CHAR(GEN_DATUM, 'yyyy') -- the most undistinctive (1)
ELSE
NULL
END
=
CASE
WHEN :DATUM_MODUS = '#WO' THEN TO_CHAR(:DATUM, 'dd.mm.yyyy')
WHEN :DATUM_MODUS = '#KW' THEN TO_CHAR(:DATUM, 'iw')
WHEN :DATUM_MODUS = '#MO' THEN TO_CHAR(:DATUM, 'mm')
WHEN :DATUM_MODUS = '#JA' THEN TO_CHAR(:DATUM, 'yyyy')
ELSE
NULL
END
--
-- If you use bind variables :DATUM_MODUS = '#KW' and :DATUM = To_Date('19.06.2022', 'dd.mm.yyyy') the result is:
-- ID GEN_DATUM WEEK_OF_GEN_DATUM MONTH_OF_GEN_DATUM YEAR_OF_GEN_DATUM DATUM_MODUS DATUM
-- ---------- ---------- ----------------- ------------------ ----------------- ----------- ----------
-- 3 17.06.2022 24 06 2022 #KW 19.06.2022
-- 4 19.06.2022 24 06 2022 #KW 19.06.2022
--
-- For :DATUM_MODUS = '#MO' and :DATUM = To_Date('14.01.2022', 'dd.mm.yyyy') the result is:
-- ID GEN_DATUM WEEK_OF_GEN_DATUM MONTH_OF_GEN_DATUM YEAR_OF_GEN_DATUM DATUM_MODUS DATUM
-- ---------- ---------- ----------------- ------------------ ----------------- ----------- ----------
-- 1 08.01.2022 01 01 2022 #MO 14.01.2022
... and so on....
In the SELECT part there are all the values involved so you can check the results and/or (if needed) filter them even more if you make this a subquery of a main one. In that case you can manipulate the data further more. Regards...