Update table based on sub select of two other tables - mysql

Question

I'm really new here and I really need help. I am trying to update a table based on data joined from another select statement.
SELECT DISTINCT A.business_unit_AP
, A.VOUCHER_ID
, A.JOURNAl_ID
, A.UNPOST_SEQ
, A.APPL_JRNL_ID
, A.PYMNT_CNT
, A.VOUCHER_LINE_NUM
, A.DISTRIB_LINE_NUM,A.dst_acct_type
, A.LEDGER
, A.PROCESS_INSTANCE
FROM PS_PROJ_RES_TMP A
LEFT OUTER JOIN ps_proj_res_cal_vw B
ON a.business_unit_ap = B.BUSINESS_UNIT_AP
AND B.PROJECT_ID = A.PROJECT_ID
AND A.ACTIVITY_ID = B.ACTIVITY_ID
AND A.RESOURCE_ID = B.RESOURCE_ID
WHERE A.SYSTEM_SOURCE ='BAP'
AND b.business_unit_ap is null*
So basically the statement above select data from PS_PROJ_RES_TMP table that doesn't exist in PS_PROJ_RES_CAL_VW. Am i right? Then based on the data pulled, I will then update PS_VCHR_ACCTG_LINE.
I formulated this script but its taking too long. And i ended up updating the whole table.
UPDATE PS_VCHR_ACCTG_LINE C
SET C.PC_DISTRIB_STATUS = 'N'
WHERE EXISTS
(
SELECT DISTINCT A.business_unit_AP
, A.VOUCHER_ID
, A.JOURNAl_ID
, A.UNPOST_SEQ
, A.APPL_JRNL_ID
, A.PYMNT_CNT
, A.VOUCHER_LINE_NUM
, A.DISTRIB_LINE_NUM
, A.dst_acct_type
, A.LEDGER
, A.PROCESS_INSTANCE
FROM PS_PROJ_RES_TMP A
LEFT OUTER JOIN ps_proj_res_cal_vw B
ON a.business_unit_ap = B.BUSINESS_UNIT_AP
AND B.PROJECT_ID = A.PROJECT_ID
AND A.ACTIVITY_ID = B.ACTIVITY_ID
AND A.RESOURCE_ID = B.RESOURCE_ID
WHERE b.business_unit_ap is null
AND b.PROJECT_ID is null
AND b.ACTIVITY_ID is null
AND b.RESOURCE_ID is null
AND C.BUSINESS_UNIT = a.business_unit_ap
AND C.VOUCHER_ID = A.VOUCHER_ID
AND C.unpost_seq = A.unpost_seq
AND c.appl_jrnl_id = A.appl_jrnl_id
AND c.PYMNT_CNT = A.pymnt_cnt
AND C.voucher_line_num = A.voucher_line_num
AND C.distrib_line_num = A.distrib_line_num
AND C.dst_acct_type = A.dst_acct_type
AND C.ledger = A.ledger
AND A.SYSTEM_SOURCE ='BAP'
);
Where did i go wrong? Thank you so much for the help :)

Answer 1

It is pretty much impossible for an outsider to figure out the issues with your query. The problem of updating all the rows would seem to be because the logic in the query, on the data in the table, causes a match for all rows.
There is one easy thing you can do to improve performance. The distinct is not necessary when using exists. So the following should be equivalent:
UPDATE PS_VCHR_ACCTG_LINE C
SET C.PC_DISTRIB_STATUS = 'N'
WHERE EXISTS
(
SELECT 1
FROM PS_PROJ_RES_TMP A
LEFT OUTER JOIN ps_proj_res_cal_vw B
ON a.business_unit_ap = B.BUSINESS_UNIT_AP
AND B.PROJECT_ID = A.PROJECT_ID
AND A.ACTIVITY_ID = B.ACTIVITY_ID
AND A.RESOURCE_ID = B.RESOURCE_ID
WHERE b.business_unit_ap is null
AND b.PROJECT_ID is null
AND b.ACTIVITY_ID is null
AND b.RESOURCE_ID is null
AND C.BUSINESS_UNIT = a.business_unit_ap
AND C.VOUCHER_ID = A.VOUCHER_ID
AND C.unpost_seq = A.unpost_seq
AND c.appl_jrnl_id = A.appl_jrnl_id
AND c.PYMNT_CNT = A.pymnt_cnt
AND C.voucher_line_num = A.voucher_line_num
AND C.distrib_line_num = A.distrib_line_num
AND C.dst_acct_type = A.dst_acct_type
AND C.ledger = A.ledger
AND A.SYSTEM_SOURCE ='BAP';
If your original query runs quickly, then I would suggest putting the results in a temporary table and using that for the update.
I would speculate that the performance problem is actually due to ps_proj_res_cal_vw, which I further speculate is a view of some sort. MySQL doesn't always do a good job with optimizing views.