我必須修改一個選擇oracle有人這樣做...我需要了解...我認爲這是一個糟糕的選擇,但我不知道:甲骨文可能錯誤在選擇與全外部聯接
FROM user01.myTable FULL OUTER JOIN user01.myTablemyTable_alias2
SELECT
myTable.field1 AS field1,
myTable.date_hour AS date_hour,
myTable.HOUR,
DECODE (
myTable.aux1, 'CAT', 'CAT3', myTable.aux1
) AS aux1,
myTable.sum_count,
myTable_alias2.sum_count AS sum_countx,
myTable.aux2,
myTable_alias2.aux2 AS aux2x
FROM user01.myTable FULL OUTER JOIN user01.myTable myTable_alias2
ON (myTable.field1 = myTable_alias2.field1
AND myTable.HOUR = myTable_alias2.HOUR
AND myTable.aux1 = myTable_alias2.aux1
AND TO_CHAR (TO_DATE (myTable.date_hour, 'YYYYMMDD') - 7,'YYYYMMDD') = myTable_alias2.date_hour
)
有一個在我的系統中user01.myTable,但在我的系統還沒有一個myTable_alias2。 如果我用myTable_aliasXXX替換所有myTable_alias2,請選擇正確的工作!
我不明白,我認爲myTable_alias2就像user01.myTable的副本,但如果是對的,我可以寫所有這樣的:
SELECT
myTable.field1 AS field1,
myTable.date_hour AS date_hour,
myTable.HOUR,
DECODE (myTable.aux1, 'CAT01L0', 'CAT01L03', myTable.aux1) AS aux1,
myTable.sum_count,
myTable.aux2
FROM user01.myTable
在什麼,我錯了嗎?我不明白?是特別是全外連接還是一個簡單的錯誤? 非常感謝您的時間!