Return results of query based on todays date in SQL (MySQL) Part 2

问题

I posted another question which was resolved perfectly however I now need to apply the same code I was given to a different piece of MySQL code.

What I have is

SELECT value, COUNT(*) AS 'num' 
FROM table_c 
WHERE table_c_id IN (9, 17, 25)
GROUP BY value

What I would like to do now is only show the results if they have been entered on the current date?

The current code snippet I have for checking the current date, which works great is (the date is in unixtime format)

( xxxxxxxxxxxxxx and curdate() = date( from_unixtime( b.crm_date_time_column ) ) )

The problem I have with query this is the date column is located in a totally different table, table_a.

How do I write the MySQL to check table_a for the date and apply the existing date SQL I have?

This is a MySQL database.

Any help will be gratefully received! This is way over my head!

回答1:

You'll want to first JOIN the other table onto the first using related columns (I'm assuming id in the other table is related to table_c_id).

And as I had stated in my answer to your previous question, you're better off making the comparison on the bare datetime column so that the query remains sargable(i.e. able to utilize indexes):

SELECT     a.value
FROM       table_c a
INNER JOIN table_a b ON a.table_c_id = b.id
WHERE      a.table_c_id IN (9,17,25) AND
           b.crm_date_time_column >= UNIX_TIMESTAMP(CURDATE())
GROUP BY   a.value 

This assumes the crm_date_time_column will never contain times which are in the future (e.g. tomorrow, next month, etc.), but if it can, you would just add:

AND b.crm_date_time_column < UNIX_TIMESTAMP(CURDATE() + INTERVAL 1 DAY)

as another condition in the WHERE clause.

回答2:

SELECT   c.value
FROM     table_c c, table_a a
WHERE    c.id IN (9, 17, 25)
 AND     b.crm_date_time_column >= UNIX_TIMESTAMP(CURDATE())
 AND     c.id = a.id
GROUP BY c.value

You could do it with query like this. It selects rows from both of the tables, checks if they have same ID and current date is table_a's, crm_date_time_column. I'm not sure how do you know which rows are linking to each other in your system, so it checks there if they have the same id.

来源：https://stackoverflow.com/questions/11495713/return-results-of-query-based-on-todays-date-in-sql-mysql-part-2