MySQL selecting yesterday's date

Question

How can I display and count the values whose dates are yesterday? I used time() to insert date in the database. Example:

URL: google.com youtube.com google.com youtube.com test.com youtube.com
DateVisited: 1313668492 1313668540 1313668571 13154314

I want do display how many URLs that have multiple existed in the table and also how many of that URL have been visited yesterday. Example result:

LINK       | timesExisted | timesVisitedYesterday
Google.com |       2      | 2
youtube.com|       3      | 3

I already have the idea on getting yesterday's date, but I don't have an idea on counting how many times a URL has existed for yesterday and counting how many times a URL has existed in the table.

Answer 1

The simplest and best way to get yesterday's date is:

subdate(current_date, 1)

Your query would be:

SELECT 
    url as LINK,
    count(*) as timesExisted,
    sum(DateVisited between UNIX_TIMESTAMP(subdate(current_date, 1)) and
        UNIX_TIMESTAMP(current_date)) as timesVisitedYesterday
FROM mytable
GROUP BY 1

For the curious, the reason that sum(condition) gives you the count of rows that satisfy the condition, which would otherwise require a cumbersome and wordy case statement, is that in mysql boolean values are 1 for true and 0 for false, so summing a condition effectively counts how many times it's true. Using this pattern can neaten up your SQL code.