sql查询最新日期

Question

I am listing item from a database, in an array of many database items. I know what I am trying to do can be done by having separate table, however for this requirement, i wanted to see if it is possible to do the following.

My code is:

$sql_list  ="SELECT  *
    FROM ".$this->tables_rma."
    ORDER BY dateCreated DESC";

This returns an array of data in the table which is good, however I have multiple entries of the same item with different entities.

So what i want to be able to do is select one of each entry, by its most recently updated row of data.

Is this possible, or am i simply trying to cut corners?

Answer 1

您可以使用SELECT DISTINCT [column]或GROUP BY [column]

Answer 2

Something like this with LIMIT 1?

$sql_list  ="SELECT  *
    FROM ".$this->tables_rma."
    ORDER BY dateCreated DESC LIMIT 1";

Answer 3

Suppose you have ID unique field and YourITEM field then:

select * from YourTable t1 where id = 
   (select id from YourTable t2 
     where t2.YourItem=t1.YourItem 
     order by DateCreated desc, id desc limit 1)

If you don't need last DateCreated value in your select then just:

select distinct YourItem from YourTable;