sum()
sum(case when CONDITION or[and] then EXEPRESS [else EXPRESS_OTHER] end )
Example :select sum(case when score<'80' and score>'60' then total end) from student_score_tbl;
nlssort()
'NLS_SORT = SCHINESE_PINYIN_M' 按拼音
'NLS_SORT = SCHINESE_STROKE_M' 按筆畫
'NLS_SORT = SCHINESE_RADICAL_M' 按部首
Example: select * from student_score_tbl order by nlssort ( student_name,'NLS_SORT=SCHINESE_RADICAL_M');
decode()
Example :Select * from student_score_tbl order by decode(class_name, '一班','1','二班','2','三班','3','四班','4');
insert into vl_test values ('中國人ab','中國人ab');
select nvarchar_test,varchar_test,length(nvarchar_test),length(varchar_test),
lengthb(nvarchar_test),lengthb(varchar_test) from vl_test;
可以看出nvarchar2是按照Unicode編碼存儲，varchar2是按照實際佔用空間存儲。
