Oracle SQL函数之字符串函数

1.SQL> select ASCII('a'),ASCII('A'),CHR() from dual; --ASCLL（x）返回x的ASCLL码，CHR(x)返回ASCLL码为x的字符
ASCII('A') ASCII('A') CHR()
---------- ---------- -------
                  a

2.SQL> SELECT NAME,INSTR(NAME,'Science') FROM PRODUCTS WHERE PRODUCT_ID=;  --显示字符串Science出现的位置
NAME                           INSTR(NAME,'SCIENCE')
------------------------------ ---------------------
Modern Science                                     

3.SQL>  SELECT NAME,INSTR(NAME,'e',1,2) FROM PRODUCTS WHERE NAME LIKE'%e%e%';  --1表示从第1个字符开始，2表示出现次数2次
NAME                           INSTR(NAME,'E',,)
------------------------------ -------------------
Modern Science
: The Return
Space Force
From Another Planet
Creative Yell                                    

4.SQL>  SELECT CONCAT(FIRST_NAME || ' ', LAST_NAME) FROM CUSTOMERS; --concat(x,y)连接字符串xy
CONCAT(FIRST_NAME||'',LAST_NAM
------------------------------
Cynthis Green
JOHN BROWN
Doreen Blue
Steve White
GAIL BLACK
%test test
 rows selected

5.SQL> SELECT INITCAP(DESCRIPTION)  FROM PRODUCTS WHERE PRODUCT_ID<;   --inicat(x)，首字母大写
INITCAP(DESCRIPTION)
--------------------------------------------------
A Description Of Modern Science
Introduction To Chemistry

6.SQL> SELECT LENGTH(NAME) FROM PRODUCTS; --length(x），返回x的长度
LENGTH(NAME)
------------

 rows selected

7.SQL> SELECT NAME,LOWER(NAME),UPPER(NAME) FROM PRODUCTS;  --转换为大小写
NAME                           LOWER(NAME)                    UPPER(NAME)
------------------------------ ------------------------------ ------------------------------
Modern Science                 modern science                 MODERN SCIENCE
Chemistry                      chemistry                      CHEMISTRY
Supernova                      supernova                      SUPERNOVA
Tank War                       tank war                       TANK WAR
Z Files                        z files                        Z FILES
: The Return               : the return               : THE RETURN
Space Force                   space force                   SPACE FORCE
From Another Planet            from another planet            FROM ANOTHER PLANET
Classical Music                classical music                CLASSICAL MUSIC
Pop                           pop                           POP
Creative Yell                  creative yell                  CREATIVE YELL
My Front Line                  my front line                  MY FRONT LINE
 rows selected

8.SQL> SELECT RPAD(NAME,20,'-'),LPAD(PRICE,10,'*') FROM PRODUCTS;  --RPAD(x，width,string)右填充，RPAD(x,width,string)左填充
RPAD(NAME,,'-')                        LPAD(PRICE,,'*')
---------------------------------------- --------------------
Modern Science------                     *****19.95
Chemistry-----------                     ********
Supernova-----------                     *****25.99
Tank War------------                     *****13.95
Z Files-------------                     *****49.99
: The Return----                     *****14.95
Space Force -------                     *****13.49
From Another Planet-                     *****12.99
Classical Music-----                     *****10.99
Pop ---------------                     *****15.99
Creative Yell-------                     *****14.99
My Front Line-------                     *****13.49
 rows selected

9.SQL> SELECT LTRIM('    HELLO RUSKY'),RTRIM('HELLO RUSKY ABCDE','EDCB'),TRIM('AB' FROM 'ABC HELLO RUSKY ABCDEA') FROM DUAL;
SELECT LTRIM('    HELLO RUSKY'),RTRIM('HELLO RUSKY ABCDE','EDCB'),TRIM('AB' FROM 'ABC HELLO RUSKY ABCDEA') FROM DUAL
ORA-30001: 截取集仅能有一个字符

SQL> SELECT LTRIM('    HELLO RUSKY'),RTRIM('HELLO RUSKY ABCDE','EDCB'),TRIM('A' FROM 'ABC HELLO RUSKY ABCDEA') FROM DUAL;
LTRIM('HELLORUSKY') RTRIM('HELLORUSKYABCDE','EDCB' TRIM('A'FROM'ABCHELLORUSKYABCD
------------------- ------------------------------ ------------------------------
HELLO RUSKY         HELLO RUSKY A                  BC HELLO RUSKY ABCDE

SQL> select ltrim('abcdefg','abc')from dual;
  LTRIM('ABCDEFG','ABC')
  ----------------------
  defg

说明：LTRIM(x,string)从X左边开始截去string中的字符串  RTRIM(x,string)从X右边开始截去string中的字符串   TRIM(string FROM x)从x的左右两边截去string   这三个函数，如果不指定string，则默认截去x中的空格。

10.SQL> SELECT CUSTOMER_ID,NVL(PHONE,'Unknown Phone Number') FROM CUSTOMERS;   --NVL(x,value),如果x为空，则返回values
                            CUSTOMER_ID NVL(PHONE,'UNKNOWNPHONENUMBER'
--------------------------------------- ------------------------------
                                       --

                                       Unknown Phone Number
                                       --

                                       Unknown Phone Number
 rows selected

11.SQL> SELECT CUSTOMER_ID,NVL2(PHONE,'Known','Unknown') FROM CUSTOMERS; --NVL2(x,value1,value2)如果x非空，返回value1,如果x为空，返回value2
                            CUSTOMER_ID NVL2(PHONE,'KNOWN','UNKNOWN')
--------------------------------------- -----------------------------
                                       Known
                                       Known
                                       Unknown
                                       Known
                                       Known
                                       Unknown
 rows selected

12.SQL> SELECT NAME,REPLACE(NAME,'Science','Physics') FROM PRODUCTS WHERE PRODUCT_ID=; --REPLACE(x,search_string,replace_string),在x中查找search_string,并替换为replace_string
NAME                           REPLACE(NAME,'SCIENCE','PHYSIC
------------------------------ --------------------------------------------------------------------------------
Modern Science                 Modern Physics

13.SQL> SELECT LAST_NAME FROM CUSTOMERS WHERE SOUNDEX(LAST_NAME)=SOUNDEX('WHYTE'); --SOUNDEX(x)查找发音相似的单词
LAST_NAME
----------
White

14.SQL> SELECT NAME,SUBSTR(NAME,2,7) FROM PRODUCTS;   --SUBSTR(x,start,length)从x中的start位置，截取指定长度length的字符
NAME                           SUBSTR(NAME,,)
------------------------------ ----------------
Modern Science                 odern S
Chemistry                      hemistr
Supernova                      upernov
Tank War                       ank War
Z Files                         Files
: The Return               : Th
Space Force                   pace Fo
From Another Planet            rom Ano
Classical Music                lassica
Pop                           op
Creative Yell                  reative
My Front Line                  y Front
 rows selected

15.SQL> SELECT NAME,SUBSTR(NAME,2) FROM PRODUCTS;  --如果不指定length，则从第2个字符截取后面全部
NAME                           SUBSTR(NAME,)
------------------------------ ----------------------------------------------------------
Modern Science                 odern Science
Chemistry                      hemistry
Supernova                      upernova
Tank War                       ank War
Z Files                         Files
: The Return               : The Return
Space Force                   pace Force
From Another Planet            rom Another Planet
Classical Music                lassical Music
Pop                           op
Creative Yell                  reative Yell
My Front Line                  y Front Line
 rows selected

15.SQL> SELECT NAME,UPPER(SUBSTR(NAME,2,8)) FROM PRODUCTS;  --使用组合函数
NAME                           UPPER(SUBSTR(NAME,,))
------------------------------ -----------------------
Modern Science                 ODERN SC
Chemistry                      HEMISTRY
Supernova                      UPERNOVA
Tank War                       ANK WAR
Z Files                         FILES
: The Return               : THE
Space Force                   PACE FOR
From Another Planet            ROM ANOT
Classical Music                LASSICAL
Pop                           OP
Creative Yell                  REATIVE
My Front Line                  Y FRONT
 rows selected