Oracle Isolation Levels : Read committed (315)

This is the default transaction isolation level. Each query executed
by a transaction sees only data that was committed before the
query (not the transaction) began. An Oracle query never reads
dirty (uncommitted) data.
Because Oracle does not prevent other transactions from
modifying the data read by a query, that data can be changed by
other transactions between two executions of the query. Thus, a
transaction that runs a given query twice can experience both nonrepeatable read and
phantoms.

Oracle隔離級別 : 已提交讀取
1. Oracle預設的事務隔離級別
2. 事務內執行的查詢只能看到查詢執行前就已經提交的資料. Oracle 的查詢永遠不會讀取髒資料

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