DATEDIFF function in Oracle

问题

I need to use Oracle but DATEDIFF function doesn't work in Oracle DB.

How to write the following code in Oracle? I saw some examples using INTERVAL or TRUNC.

SELECT DATEDIFF ('2000-01-01','2000-01-02') AS DateDiff;

回答1:

In Oracle, you can simply subtract two dates and get the difference in days. Also note that unlike SQL Server or MySQL, in Oracle you cannot perform a select statement without a from clause. One way around this is to use the builtin dummy table, dual:

SELECT TO_DATE('2000-01-02', 'YYYY-MM-DD') -  
       TO_DATE('2000-01-01', 'YYYY-MM-DD') AS DateDiff
FROM   dual

回答2:

Just subtract the two dates:

select date '2000-01-02' - date '2000-01-01' as dateDiff
from dual;

The result will be the difference in days.

More details are in the manual:
https://docs.oracle.com/cd/E11882_01/server.112/e41084/sql_elements001.htm#i48042

回答3:

You can simply subtract two dates. You have to cast it first, using to_date:

select to_date('2000-01-01', 'yyyy-MM-dd')
       - to_date('2000-01-02', 'yyyy-MM-dd')
       datediff
from   dual
;

The result is in days, to the difference of these two dates is -1 (you could swap the two dates if you like). If you like to have it in hours, just multiply the result with 24.

回答4:

We can directly subtract dates to get difference in Days.

    SET SERVEROUTPUT ON ;
    DECLARE
        V_VAR NUMBER;
    BEGIN
         V_VAR:=TO_DATE('2000-01-02', 'YYYY-MM-DD') - TO_DATE('2000-01-01', 'YYYY-MM-DD') ;
         DBMS_OUTPUT.PUT_LINE(V_VAR);
    END;

来源：https://stackoverflow.com/questions/28406397/datediff-function-in-oracle

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sql

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datediff