pl/sqlµÄcase whenÔõôÓÃÄØ£¿

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select case when ... then
...
else case when .... then
....
else
null
end from ...

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else case when .... then
Õâ¸öÀïÃæµÄcase½áÊøʱÊÇ·ñ¼ÓÁËend

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select      case when ... then
            ...
        else case when ....  then
              ....
        else
          null
        end  from ...

else ºóÃæ²»ÓÃÔÚ¼ÓcaseÁË.

Óï·¨ÊÇ:
select case
when ... then ...
...
else
null
end
from t

---

SELECT col1, col2,
CASE
WHEN col3 > 1 AND col3 <2
THEN '1'
WHEN col3 > 2 AND col3 <3
THEN '2'
WHEN col3 > 3 AND col3 <4
THEN '3'
ELSE '4'
END mylevel
from table1

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1¡¢ÒÔCASE¿ªÍ·£¬ÒÔEND½áβ
2¡¢·ÖÖ§ÖÐWHEN ºó¸úÌõ¼þ£¬THENΪÏÔʾ½á¹û
3¡¢ELSE Ϊ³ý´ËÖ®ÍâµÄĬÈÏÇé¿ö£¬ÀàËÆÓڸ߼¶ÓïÑÔ³ÌÐòÖÐswitch caseµÄdefault£¬¿ÉÒÔ²»¼Ó
4¡¢END ºó¸ú±ðÃû

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SQL code
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