如何在SQL中获得日期之间的差异

Question

I have seen other answers but my question is different because I want to get the difference between two dates and use it in the where clause but its asking me to enter days to get difference. The dates are coming from my database.

Select datediff(D, cid, ced) as theDateDiff
from customers 

Select datediff(D, cid, ced) as theDateDiff
from customers where theDateDiff>=5

Answer 1

假设cid和ced是customers表中的字段，则不妨尝试以下操作：

select * from customers c where datediff("d", c.cid, c.ced) >= 5

Answer 2

Consider following two issues involving your MS Access SQL:

1. In most cases with some exceptions, you cannot use an alias of a calculated column in other parts of same level query. You can however use such an alias if residing in another query or subquery.

    SELECT * FROM (SELECT *, DateDiff("d", cid, ced) AS theDateDiff FROM customers) sub where theDateDiff >= 5 

2. The DateDiff function in MS Access differs from the DateDiff of SQL Server where the latter appears to be the version you use with unquoted D as first argument. Remember no two dialects in the relational database world are exactly alike even if under same parent company.

   Therefore, replace DateDiff(D, cid, ced) with DateDiff("d", cid, ced) .

   To cite another example other than Microsoft, Oracle (company) now manages MySQL which is a very different RDBMS with much different dialect than flagship database: Oracle.