Oracle单值函数.docVIP

单值函数（看到函数需要知道有什么功能，能根据功能选择相应函数） lpad()函数：用于格式化代码 SQL select lpad(21,6,0) stock_code from dual; STOCK_ 21为原始数据，6为格式化后的位数， ------ 0是填充的字符，填充在数据左边 000021 SQL select lpad(1234567,6,0) stock_code from dual; STOCK_ ------ 123456 rpad()函数：从数据右端补齐字符串 SQL select rpad(abc, 10, *) from dual; RPAD(ABC ---------- abc******* SQL select rpad(abcdefg, 6, *) from dual; RPAD( ------ abcdef lower()函数：返回小写字符串 SQL select sid,sname from tab_student where lower(sname)=lower(tom); SID SNAME ---------- -------------------- 1 Tom upper（）函数：返回大写字符串 SQL select sid,sname from tab_student where upper(sname)=upper(TOM); SID SNAME ---------- -------------------- 1 Tom initcap ()函数：单词首字母大写 SQL select initcap(big) from dual; INI --- Big SQL select initcap(bigbigtiger) from dual; INITCAP(BI ----------- Bigbigtiger SQL select initcap(big_big_tiger) from dual; INITCAP(BIG_ ------------- Big_Big_Tiger SQL select initcap(big/big/tiger) from dual; INITCAP(BIG/ ------------- Big/Big/Tiger SQL select initcap(big big tiger) from dual; INITCAP(BIGB ------------- Big Big Tiger length()函数：返回字符串长度 SQL select length(abcd ) from dual; LENGTH(ABCD) -------------- 8 SQL select length() from dual; LENGTH() ---------- SQL select length(12.51) from dual; LENGTH(12.51) ------------- 5 substr函数（）：截取字符串 SQL select substr(1234567890, 5, 4) from dual; SUBS 对1234567890截取自第五位开始的4个字符 ---- 5678 SQL select substr(1234567890, 5) from dual; SUBSTR ------ 567890 instr()函数：获得子字符串在父字符串中出现的位置 SQL select instr(big big tiger, big) from dual; INSTR(BIGBIGTIGER,BIG) -------------------------- 1 SQL select instr(big big tiger, big, 2) from dual; INSTR(BIGBIGTIGER,BIG,2) ---------------------------- 5 SQL select instr(big big tiger, big, 2, 2) from dual; INSTR(BIGBIGTIGER,BIG,2,2) ------------------------------ 0 ltrim（）