SQL> create table t1(a varchar(10));

Table created.

SQL> insert into t1 values ('12.3456');

1 row created.

SQL> select round(a) from t1;

  ROUND(A)
----------
      12

SQL> select round(a,3) from t1;

ROUND(A,3)
----------
12.346

SQL> select cast(a as int) from t1;

CAST(AASINT)
------------
      12

SQL> select cast(a as number(8,4)) from t1;

CAST(AASNUMBER(8,4))
--------------------
         12.3456

=========================================================

cast 是进行类型转换的, 可以针对各种Oracle数据类型. 修改的是用户的数据类型.

round只是修改的数据显示格式. 对数据做四舍五入. 类似的函数还有ceil(取此数据的最小整数). trunc( 取整函数.)

复制内容到剪贴板代码:SQL> select round(12.45) round,trunc(12.45) trunc,ceil(12.45) ceil
  2  from dual
  3  /

   ROUND    TRUNC    CEIL
---------- ---------- ----------
      12       12       13

SQL> select round(12.54) round,trunc(12.54) trnc,ceil(12.54) ceil
  2  from dual
  3  /

   ROUND    TRNC    CEIL
---------- ---------- ----------
      13       12       13

SQL>

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cast 函数

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