Oracle 如何获取sqlcl中字符串的长度

我试图根据名称中字符串的长度显示前三行。但是系统只读取字符串列的预定义长度，而不是列中的字符串

SQL> select max(length(name)) from cus_detail;

---

这就是

CHAR

datatype所做的-它用空格右键填充值，直到整列长度：

SQL> create table test (name char(10));

Table created.

SQL> insert into test (name) values ('London');

1 row created.

SQL> select max(length(name)) from test;

MAX(LENGTH(NAME))
-----------------
               10

SQL>

近距离观察：

SQL> select '#' || name ||'#' name, dump(name) dmp from test;

NAME         DMP
------------ --------------------------------------------------
#London    # Typ=96 Len=10: 76,111,110,100,111,110,32,32,32,32
       ^^^^                 L  o   n   d   o   n   ^^^^^^^^^^^
       spaces                                      spaces

因此，您可以

trim

该值：

SQL> select max(length(trim(name))) from test;

MAX(LENGTH(TRIM(NAME)))
-----------------------
                      6

SQL>

或者-甚至更好-将列的数据类型更改为

varchar2

SQL> create table test (name char(10));

Table created.

SQL> insert into test (name) values ('London');

1 row created.

SQL> select max(length(name)) from test;

MAX(LENGTH(NAME))
-----------------
               10

SQL>

SQL> select '#' || name ||'#' name, dump(name) dmp from test;

NAME         DMP
------------ --------------------------------------------------
#London    # Typ=96 Len=10: 76,111,110,100,111,110,32,32,32,32
       ^^^^                 L  o   n   d   o   n   ^^^^^^^^^^^
       spaces                                      spaces

SQL> select max(length(trim(name))) from test;

MAX(LENGTH(TRIM(NAME)))
-----------------------
                      6

SQL>