Sql Oracle-使用max()重构子查询
我有下面的问题。软件开发周期有多行,但我对最新的有兴趣 我想重写查询,以便不使用子查询。我已经尝试过了,但没有成功 有人能给我建议吗?多谢各位Sql Oracle-使用max()重构子查询,sql,oracle,refactoring,subquery,analytic-functions,Sql,Oracle,Refactoring,Subquery,Analytic Functions,我有下面的问题。软件开发周期有多行,但我对最新的有兴趣 我想重写查询,以便不使用子查询。我已经尝试过了,但没有成功 有人能给我建议吗?多谢各位 SELECT SOF.VENDOR, SOF.NAME, LAN.LANGUAGE, SOF.VERSION, SDC.STATUS, SDC.SOF_DC_ID FROM SOFTWARE SOF JOIN SOFTWARE_LANGUAGES SL ON
SELECT SOF.VENDOR,
SOF.NAME,
LAN.LANGUAGE,
SOF.VERSION,
SDC.STATUS,
SDC.SOF_DC_ID
FROM SOFTWARE SOF
JOIN SOFTWARE_LANGUAGES SL
ON (SL.SOF_SOF_ID = SOF.SOF_ID)
JOIN LANGUAGES LAN
ON (SL.LAN_LAN_ID = LAN.LAN_ID)
JOIN SOFTWARE_DEVELOPMENT_CYCLE SDC
ON (SDC.SOF_LAN_SOF_LAN_ID = SL.SOF_LAN_ID)
WHERE SDC.SOF_DC_ID IN (SELECT MAX(SDC2.SOF_DC_ID)
FROM SOFTWARE_DEVELOPMENT_CYCLE SDC2
WHERE SDC2.SOF_LAN_SOF_LAN_ID = SL.SOF_LAN_ID)
ORDER BY SOF.VENDOR,
SOF.NAME,
LAN.LANGUAGE,
SOF.VERSION;
您可以这样做,以避免再次点击
软件开发周期
表
SELECT vendor,
name,
language,
version,
status,
sof_dc_id
FROM (SELECT SOF.VENDOR,
SOF.NAME,
LAN.LANGUAGE,
SOF.VERSION,
SDC.STATUS,
SDC.SOF_DC_ID,
RANK() OVER (PARTITION BY sl.sdf_lan_id
ORDER BY sdc.sdf_dc_id DESC) rnk
FROM SOFTWARE SOF
JOIN SOFTWARE_LANGUAGES SL
ON (SL.SOF_SOF_ID = SOF.SOF_ID)
JOIN LANGUAGES LAN
ON (SL.LAN_LAN_ID = LAN.LAN_ID)
JOIN SOFTWARE_DEVELOPMENT_CYCLE SDC
ON (SDC.SOF_LAN_SOF_LAN_ID = SL.SOF_LAN_ID))
WHERE rnk = 1
ORDER BY VENDOR,
NAME,
LANGUAGE,
VERSION;
RANK
分析函数通过sl.sdf_lan_id
对结果集进行分区。然后,对于每个不同的sl.sdf\u lan\u id
,它将根据sdc.sdf\u dc\u id
的降序为行分配一个数字秩。这意味着对于特定的sl.sdf\u lan\u id
具有最大sdc.sdf\u dc\u id
的行的秩将为1。然后,外部其中rnk=1
谓词只选择具有该最大值的行。这应该完成与您的MAX
子查询相同的任务。谢谢。你能解释一下你决定怎么做的过程吗?