SQL中round（）函数用法

round有两个重载,一个有带有两个参数的,一个是带有三个参数的,

每一个参数都相同是要处理的数,

1.带有两个参数.每二个参数是小数点的左边第几位或右边第几位,分别用正负表示.左边为负,右边为负.为四舍五入.

select round(748.585929,-1) 750.000000

select round(748.585929,2) 748.590000

2.带三个参数.第二个参数同上.第三个参数有两种可能,一种是取0为四舍五入.另一种是正负值,则为舍去

 select round(748.585929,3,0)  748.586000

select round(748.585929,3,1)  748.585000

select round(748.585929,3,-1)  748.585000
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TEST@ORA1] SQL>select round(4321,-3) from dual;

ROUND(4321,-3)
--------------
          4000

[TEST@ORA1] SQL>select round(20,-3) from dual;

ROUND(20,-3)
------------
           0

[TEST@ORA1] SQL>select round(4500,-3) from dual;

ROUND(4500,-3)
--------------
          5000