一、Lpad函式

lpad函式將左邊的字串填充一些特定的字元其語法格式如下：lpad(string,n,[pad_string])

string:字元或者引數

n:字元的長度，是返回的字串的數量，如果這個數量比原字串的長度要短，lpad函式將會把字串擷取成從左到右的n個字元;

pad_string:可選引數，這個字串是要貼上到string的左邊，若這個引數未寫，lpad函式將會在string的左邊貼上空格。

select lpad('tech', 7) from dual; 將返回' tech'
select lpad('tech', 2) from dual; 將返回'te'
select lpad('tech', 8, '0') from dual; 將返回'0000tech'
select lpad('tech on the net', 15, 'z') from dual; 將返回'tech on the net'
select lpad('tech on the net', 16, 'z') from dual; 將返回'ztech on the net'

SQL> select lpad('tech', 7) from dual;

LPAD('T
-------
tech

SQL> select lpad('tech', 2) from dual;

LP
--
te

SQL> select lpad('tech', 8, '0') from dual;

LPAD('TE
--------
0000tech

SQL> select lpad('tech on the net', 15, 'z') from dual;

LPAD('TECHONTHE
---------------
tech on the net

SQL> select lpad('tech on the net', 16, 'z') from dual;

LPAD('TECHONTHEN
----------------
ztech on the net

SQL>

二、Rpad函式

rpad函式將右邊的字串填充一些特定的字元其語法格式如下：rpad(string,n,[pad_string])

string：字元或者引數

n：字元的長度，是返回的字串的數量，如果這個數量比原字串的長度要短，lpad函式將會把字串擷取成從左到右的n個字元;

pad_string：可選引數，這個字串是要貼上到string的右邊，如果這個引數未寫，lpad函式將會在string的右邊貼上空格。

select rpad('tech', 7) from dual; 將返回' tech'
select rpad('tech', 2) from dual; 將返回'te'
select rpad('tech', 8, '0') from dual; 將返回'tech0000'
select rpad('tech on the net', 15, 'z') from dual; 將返回'tech on the net'
select rpad('tech on the net', 16, 'z') from dual; 將返回'tech on the netz'

SQL> select rpad('tech', 7) from dual;

RPAD('T
-------
tech

SQL> select rpad('tech', 2) from dual;

RP
--
te

SQL> select rpad('tech', 8, '0') from dual;

RPAD('TE
--------
tech0000

SQL> select rpad('tech on the net', 15, 'z') from dual;

RPAD('TECHONTHE
---------------
tech on the net

SQL> select rpad('tech on the net', 16, 'z') from dual;

RPAD('TECHONTHEN
----------------
tech on the netz

lpad/rpad函式

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