Hey, Oracle, "5."

SQL functions: Single-line functions, multiline functions (grouped functions)

Character function
ASCII (' a ') =>97
Chr (=>) ' A '
Initcap (' My word ') =>my Word
InStr (' Morning, ' n ', 1,1) =>4
Length (' Eric Lu Han ') =>11
Lpad (' Targ ', ten, ' * ') =>******targ
Nls_lower (' Me ') =>me
Nls_upper (My word ") => my Word
Regexp_replace () (10g)
Regexp_substr () (10g)
Replace (' searchstring_10g ', ' searchstring ', ' replacestring ') =>replacestring_10g
Rpad (' Targ ', ten, ' * ') =>targ******
substr (' Now ', 1,2) =>no
Translate (' FromTo ', ' Fromstringtotrans ', ' tostringxxxxxxxxx ') =>tostxx conversion (character, original character, corresponding character)

Date Time function
Add_months (sysdate,-12) =>18-11-03
current_date=>2004-11-18 14:27 Date time for the current session time zone (9i)
Current_timestamp date time of the current session time zone (9i)
Dbtimezone =>+08:00 Current database time zone
...

Conversion functions
Cast (sysdate as VARCHAR2) =>18-11 month-04
To_char (sysdate, ' yyyy-mm-dd ') =>2004-11-18
To_date (sysdate, ' dd-mm-yyyy ') =>18-11 month-04

Grouping functions
...

Learn these first, later in the expansion. I can't remember.