我必须离开大约14张桌子，执行时间太长 谁能告诉我如何减少时间？
$sql= "SELECT
pd.*,
pd.id AS did,
gdr.name AS region,
gds.name AS state,
gdc.name AS city,
pus.name AS user,
pus.salesheirarchy AS saleshead,
pur.name AS rname,
pc.comp_name AS cname,
pl.name AS dlevel,
plob.lob_name,
sr.itemname,
sr.fromdate,
sr.openqty AS batchopenqty,
pp.id,
pp.sfield1,
pp.attribute1,
pp.attribute2,
pp.attribute3,
pp.attribute4,
pp.attribute5,
pp.attribute6,
pp.attribute7,
pp.attribute8,
pp.attribute9,
pp.attribute10,
pu.symbol,
pg.name AS pgroup,
ppc.name AS pcategory,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-01-01' AND '$year-01-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS jan,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-02-01' AND '$year-02-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='' ) AS feb,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-03-01' AND '$year-03-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS mar,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-04-01' AND '$year-04-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS apr,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-05-01' AND '$year-05-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS may,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-06-01' AND '$year-06-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS jun,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-07-01' AND '$year-07-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS jul,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-08-01' AND '$year-08-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS aug,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-09-01' AND '$year-09-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS sep,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-10-01' AND '$year-10-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS oct,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-11-01' AND '$year-11-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS nov,
(
SELECT Sum(openqty)
FROM pre_stock_reports
WHERE fromdate BETWEEN '$year-12-01' AND '$year-12-31'
AND pre_stock_reports.itemname=sr.itemname
AND pre_stock_reports.distid = sr.distid
AND pre_stock_reports.openqty !='') AS dece
FROM pre_stock_reports AS sr
LEFT JOIN pre_products AS pp
ON sr.itemname=pp.product_name
LEFT JOIN pre_uom AS pu
ON pp.uom=pu.id
LEFT JOIN pre_product_group AS pg
ON pp.product_group=pg.id
LEFT JOIN pre_product_category AS ppc
ON pp.product_category=ppc.id
LEFT JOIN pre_distributor AS pd
ON sr.distid=pd.id
LEFT JOIN pre_company_geo_details AS gdr
ON pd.region = gdr.id
LEFT JOIN pre_company_geo_details AS gds
ON pd.state = gds.id
LEFT JOIN pre_company_geo_details AS gdc
ON pd.city = gdc.id
LEFT JOIN pre_user AS pus
ON pd.user = pus.id
LEFT JOIN pre_user AS pur
ON pus.sales_head_name = pur.id
LEFT JOIN pre_company AS pc
ON pd.company = pc.id
LEFT JOIN pre_levels AS pl
ON pd.type = pl.level_id
LEFT JOIN pre_lob AS plob
ON pd.distributor_type = plob.id
WHERE 1 $where
AND sr.fromdate BETWEEN '$year-01-01' AND '$year-12-31'
AND sr.openqty !=''
GROUP BY sr.itemname
ORDER BY sr.fromdate ASC,
gdr.name ASC,
sr.distid DESC";
感谢。