SQL Poor Performance on join query - sql

Question

i'm experiencing really poor performance with this query, probably because of my poor experience with join.
The following query have to run on a DB2 database.
SELECT A.n_ann_ord
|| A.n_prg_ord AS numeroOrdine,
DATE(B.d_ins) AS dataInserimentoEGO,
DATE(A.d_ord) AS dataInserimento,
C.n_lot_prd AS lotto,
E.t_rag_soc AS consorzio,
D.t_rag_soc AS cliente,
b.c_obu_new AS obuid,
j.c_tar AS targa,
j.c_naz AS nazione,
C.c_pos AS postazione,
CASE
WHEN B.f_ric_obu_sat = 'S' THEN 'Satellitare'
ELSE 'Non Satellitare'
END AS tipoTitolo,
F.t_des AS statoOrdine,
CASE
WHEN (SELECT 1
FROM evda.tetsau_sos_tit_mul X
WHERE x.d_ord = a.d_ord
FETCH first ROW only) = 1 THEN 'S'
ELSE 'N'
END AS SOSTITUZIONE,
DATE(G.d_ape_pro) AS aperturaLotto,
DATE(G.d_chiu_pro) AS chiusuraLotto,
DATE(G.d_com_con) AS confezionamento,
DATE(C.d_spe_spe) AS spedizione,
C.c_ide_spe AS trackingNumber,
DATE(H.d_acq_con) AS consegna
FROM evda.tetsvi_ord A
JOIN evda.tets3t_int_srv B
ON A.c_ctp_cli = B.c_ctp_cli
AND A.d_ord = B.d_ord
JOIN evda.tetski_int_con_ord C
ON A.c_ctp_cli = C.c_ctp_cli
AND A.d_ord = C.d_ord
JOIN evda.tets25_ctp D
ON C.c_ctp_cli = D.c_ctp
JOIN evda.tets25_ctp E
ON C.c_ctp_con = E.c_ctp
JOIN evda.tetsvk_sta_ord F
ON A.c_sta_ord = F.c_sta_ord
JOIN evda.tetsvp_pre_tit I
ON a.c_ctp_cli = i.c_ctp_cli
AND a.d_ord = i.d_ord
JOIN evda.tetsmj_tit_pre_est J
ON a.c_ctp_cli = j.c_ctp_cli
AND a.d_ord = j.d_ord
AND b.n_prg_tit_pre = j.n_prg
LEFT JOIN evda.tetskk_lot_prd G
ON C.n_lot_prd = G.n_lot_prd
LEFT JOIN evda.tets3u_int_srv_spe H
ON B.d_ins = H.d_ins
WHERE DATE(a.d_ord) <= CURRENT_DATE
AND DATE(a.d_ord) >= CURRENT_DATE - 30 DAYS
GROUP BY A.n_ann_ord
|| A.n_prg_ord,
DATE(B.d_ins),
DATE(A.d_ord),
C.n_lot_prd,
E.t_rag_soc,
D.t_rag_soc,
b.c_obu_new,
j.c_tar,
j.c_naz,
C.c_pos,
B.f_ric_obu_sat,
F.t_des,
a.d_ord,
DATE(G.d_ape_pro),
DATE(G.d_chiu_pro),
DATE(G.d_com_con),
DATE(C.d_spe_spe),
C.c_ide_spe,
DATE(H.d_acq_con)

Answer 1

Avoid using functions on table columns in where clause. Also, check whether "group by" is necessary as suggested by #jarlh
If d_ord is timestamp column, change where clause to
a.d_ord < timestamp( CURRENT_DATE + 1 days)
AND a.d_ord >= timestamp( CURRENT_DATE - 30 DAYS )