Question

MySQL Tables

reject_data

+-----------+-----------------+------------------+---------------+
| reject_id | reject_location | reject_equipment | reject_time   |
+-----------+-----------------+------------------+---------------+
| 1         | 7               | 6                | 1326795921000 |
+-----------+-----------------+------------------+---------------+
| 2         | 7               | 1                | 1326796641000 |
+-----------+-----------------+------------------+---------------+
| 3         | 7               | 6                | 1326799521000 |
+-----------+-----------------+------------------+---------------+
| 4         | 6               | 5                | 1326800781000 |
+-----------+-----------------+------------------+---------------+
| 5         | 7               | 3                | 1326802281000 |
+-----------+-----------------+------------------+---------------+
| 6         | 7               | 4                | 1326802941000 |
+-----------+-----------------+------------------+---------------+
| 7         | 7               | 1                | 1326814161000 |
+-----------+-----------------+------------------+---------------+
| 8         | 6               | 2                | 1328026700000 |
+-----------+-----------------+------------------+---------------+

equipment

+--------------+------------------+
| equipment_id | equipment_string |
+--------------+------------------+
| 1            | Microdoser       |
+--------------+------------------+
| 2            | Monoblock        |
+--------------+------------------+
| 3            | Valve Magnet     |
+--------------+------------------+
| 4            | Checkweigher     |
+--------------+------------------+
| 5            | Microleak        |
+--------------+------------------+
| 6            | Capper           |
+--------------+------------------+

locations

+-------------+-----------------+
| location_id | location_string |
+-------------+-----------------+
| 1           | Fred Line 1     |
+-------------+-----------------+
| 2           | Fred Line 2     |
+-------------+-----------------+
| 3           | Fred Line 3     |
+-------------+-----------------+
| 4           | Bob Line 1      |
+-------------+-----------------+
| 5           | Bob Line 2      |
+-------------+-----------------+
| 6           | Bob Line 3      |
+-------------+-----------------+
| 7           | Jeff Line 1     |
+-------------+-----------------+
| 8           | Jeff Line 2     |
+-------------+-----------------+
| 9           | Jeff Line 3     |
+-------------+-----------------+

emrs_data

+---------+---------------+-----------+-------------+---------------+
| emrs_id | emrs_location | emrs_code | emrs_string | emrs_time     |
+---------+---------------+-----------+-------------+---------------+
| 1       | 8             | 8744751   | String Text | 1331051832000 |
+---------+---------------+-----------+-------------+---------------+
| 2       | 3             | 8660465   | String Text | 1331051832000 |
+---------+---------------+-----------+-------------+---------------+
| 3       | 6             | 8665447   | String Text | 1331055356000 |
+---------+---------------+-----------+-------------+---------------+
| 4       | 7             | 8762177   | String Text | 1331060531000 |
+---------+---------------+-----------+-------------+---------------+
| 5       | 4             | 8547253   | String Text | 1331061898000 |
+---------+---------------+-----------+-------------+---------------+
| 6       | 9             | 8744580   | String Text | 1331062654000 |
+---------+---------------+-----------+-------------+---------------+
| 7       | 2             | 8668716   | String Text | 1331064810000 |
+---------+---------------+-----------+-------------+---------------+
| 8       | 1             | 8665436   | String Text | 1331066757000 |
+---------+---------------+-----------+-------------+---------------+
| 9       | 5             | 8761458   | String Text | 1331066847000 |
+---------+---------------+-----------+-------------+---------------+
| 10      | 8             | 8743520   | String Text | 1331068372000 |
+---------+---------------+-----------+-------------+---------------+
| 11      | 3             | 8708691   | String Text | 1331070587000 |
+---------+---------------+-----------+-------------+---------------+
| 12      | 7             | 8811149   | String Text | 1331071045000 |
+---------+---------------+-----------+-------------+---------------+

Current Queries

the following query is what i currently use, please note that I have used ‘IN’ because these are dynamic, same for the ‘BETWEEN’ values.

SELECT location_string, equipment_string, reject_time 
FROM reject_data, equipment, locations
WHERE reject_equipment = equipment_id 
    AND reject_location = location_id 
    AND reject_location IN (7) 
    AND reject_equipment IN (1,2,3,4,5,6) 
    AND reject_time BETWEEN 0 AND 1331113803000
ORDER BY reject_id DESC 
LIMIT 100

Question

What I would like to do is add two columns to the right containing emrs_code and emrs_string, please see the table below as an example. The problem I am having is trying to get the relevant emrs_code and emrs_string for each reject record, I only want to return one set of emrs results per reject and the emrs data needs to be from the nearest previous time compared to the reject_time, kinda hard to explain so here is a query that gets me the correct information for a predifined location and time:

SELECT emrs_code, emrs_string
FROM `rejectlogging`.`emrs_data`
WHERE emrs_time <= 1331113803000 AND emrs_location = 7
ORDER BY emrs_time DESC
LIMIT 1;

I am basically stuck at getting the above merged into the original query. Any help would be much appreciated. Thank you.

Desired Result

+-----------------+------------------+---------------+-----------+-------------+
| location_string | equipment_string | reject_time   | emrs_code | emrs_string |
+-----------------+------------------+---------------+-----------+-------------+
| A7              | Microleak        | 1331064910000 | 8762177   | String Text |
+-----------------+------------------+---------------+-----------+-------------+
| A3              | Checkweigher     | 1331107261000 | 8708691   | String Text |
+-----------------+------------------+---------------+-----------+-------------+
| A1              | Microdoser       | 1331107166000 | 8665436   | String Text |
+-----------------+------------------+---------------+-----------+-------------+
| A2              | Microdoser       | 1331107161000 | 8668716   | String Text |
+-----------------+------------------+---------------+-----------+-------------+
| A4              | Microleak        | 1331105836000 | 8547253   | String Text |
+-----------------+------------------+---------------+-----------+-------------+

Answer 1

Try this:-(UPDATED)

SELECT location_string, equipment_string, reject_time , (SELECT emrs_code
FROM `rejectlogging`.`emrs_data`
WHERE emrs_time <= reject_data.reject_time AND emrs_location = reject_data.reject_location
ORDER BY emrs_time DESC
LIMIT 1) as emrs_code,
(SELECT emrs_string
FROM `rejectlogging`.`emrs_data`
WHERE emrs_time <= reject_data.reject_time AND emrs_location = reject_data.reject_location 
ORDER BY emrs_time DESC
LIMIT 1) as emrs_string
FROM reject_data, equipment, locations
WHERE reject_equipment = equipment_id 
    AND reject_location = location_id 
    AND reject_location IN (7) 
    AND reject_equipment IN (1,2,3,4,5,6) 
    AND reject_time BETWEEN 0 AND 1331113803000
ORDER BY reject_id DESC 
LIMIT 100