1, deocde 與 case when 的作用相同，用於不同條件分支的不同處理。於case when 相比只是用法不同。同樣可以巢狀和滿足多個值。

2，多個值

decode(name, "Wang", "001", "Li", "002", "003")

相當於

case

when name = "Wang"

then "001"

when name = "Li"

then "002"

else "003"

end

3, 巢狀

decode(name, "Wang", decode(sno, "001", "Yes", ""), "Li", decode(sno,"002","Yes",""), decode(sno, "003","Yes",""))

相當於

case

when name = "Wang"

then case

when sno="001"

then "Yes"

else ""

end

when name="Li"

then case

when sno="002"

then "Yes"

else ""

end

else case

when sno="003"

then "Yes"

else ""

end

end