Oracle SQL statement operand: rounding, rounding, differentiation and formatting

use oracle sql Operate on numbers : Take up and round 、 Rounding down 、 Retain N Decimal place 、 rounding 、 Number formatting

integer （ Rounding down ）： 
select floor(5.534) from dual;
select trunc(5.534) from dual;
The above two usages can be used for numbers 5.534 Rounding down , The result is 5.

If you want to round up  , The result is 6, You should use ceil
select ceil(5.534) from dual;

 

rounding ： 
SELECT round(5.534) FROM dual;
SELECT round(5.534,0) FROM dual;
SELECT round(5.534,1) FROM dual;
SELECT round(5.534,2) FROM dual;
The results are 6,  6,  5.5,  5.53

 

Retain N Decimal place （ Do not round off ）： 
select trunc(5.534,0) from dual;
select trunc(5.534,1) from dual;
select trunc(5.534,2) from dual;
The results are 5,5.5,5.53, Where reserved 0 Decimal places are equivalent to rounding directly .

 

Number formatting ： 
select to_char(12345.123,'99999999.9999') from dual;
The result is 12345.123

select to_char(12345.123,'99999999.9900') from dual;
The third and fourth after the decimal place are insufficient 0, The result is 12345.1230

select to_char(0.123,'99999999.9900') from dual;
select to_char(0.123,'99999990.9900') from dual;
The results are .123, 0.123

 

Take a percentage

select 100*round(COUNT(*)/SUM(COUNT(*)) OVER(),4)||'%'percent FROM  Table name