Functions and trigger procedures are always executed within a transaction established by an outer query — they cannot start or commit that transaction, since there would be no context for them to execute in. However, a block containing an EXCEPTION clause effectively forms a subtransaction that can be rolled back without affecting the outer transaction.
函數(shù)和觸發(fā)過程總是在由外部查詢建立的事務(wù)中執(zhí)行——它們不能啟動(dòng)或提交該事務(wù)，因?yàn)闆]有上下文供它們?cè)谄渲袌?zhí)行。但是，包含EXCEPTION子句的塊有效地形成了一個(gè)子事務(wù)，可以在不影響外部事務(wù)的情況下回滾。