Question

I tried to simplify my question to a basic example I wrote down below, the actual problem is much more complex so the below queries might not make much sense but the basic concepts are the same (data from one query as argument to another).

Query 1:

SELECT Ping.ID as PingID, Base.ID as BaseID FROM 
    (SELECT l.ID, mg.DateTime from list l
     JOIN mygroup mg ON mg.ID = l.MyGroup
     WHERE l.Type = "ping"
     ORDER BY l.ID DESC
    ) Ping
    INNER JOIN
    (SELECT l.ID, mg.DateTime from list l
     JOIN mygroup mg ON mg.ID = l.MyGroup
     WHERE l.Type = "Base"
     ORDER BY l.ID DESC
    ) Base
    ON Base.DateTime < Ping.DateTime
    GROUP BY Ping.ID
    ORDER BY Ping.ID DESC;

+--------+--------+
| PingID | BaseID |
+--------+--------+
|     11 |     10 |
|      9 |      8 |
|      7 |      6 |
|      5 |      3 |
|      4 |      3 |
+--------+--------+

// from below I need to replace 11 by PingID above and 10 by BaseID above then the results to show up on as third column above (0 if no results, 1 if results)

Query 2:

SELECT * FROM 
    (SELECT sl.Data FROM list l 
     JOIN sublist sl ON sl.ParentID = l.ID
    WHERE l.Type = "ping" AND l.ID = 11) Ping
    INNER JOIN
    (SELECT sl.Data FROM list l 
     JOIN sublist sl ON sl.ParentID = l.ID
    WHERE l.Type = "base" AND l.ID = 10) Base
    ON Base.Data < Ping.Data;

How can I do this? Again I’m not sure what kind of advice I will receive but please understand that the Query 2 is in reality over 200 lines and I basically can’t touch it so I don’t have so much flexibility as I’d like and ideally I’d like to get this working all in SQL without having to script this.

CREATE DATABASE lookback;
use lookback;

CREATE TABLE mygroup (
ID                          BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY, 
DateTime                    DateTime    
) ENGINE=InnoDB;

CREATE TABLE list (
ID                          BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
Type                        VARCHAR(255),
MyGroup                     BIGINT NOT NULL,
Data                        INT NOT NULL
) ENGINE=InnoDB;

CREATE TABLE sublist (
ID                          BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
ParentID                    BIGINT NOT NULL,
Data                        INT NOT NULL
) ENGINE=InnoDB;

INSERT INTO mygroup (DateTime) VALUES ("2012-03-09 22:33:19"), ("2012-03-09 22:34:19"), ("2012-03-09 22:35:19"), ("2012-03-09 22:36:19"), ("2012-03-09 22:37:19"), ("2012-03-09 22:38:19"), ("2012-03-09 22:39:19"), ("2012-03-09 22:40:19"), ("2012-03-09 22:41:19"), ("2012-03-09 22:42:19"), ("2012-03-09 22:43:19");    
INSERT INTO list (Type, MyGroup, Data) VALUES ("ping", 1, 4), ("base", 2, 2), ("base", 3, 4), ("ping", 4, 7), ("ping", 5, 8), ("base", 6, 7), ("ping", 7, 8), ("base", 8, 3), ("ping", 9, 10), ("base", 10, 2), ("ping", 11, 3);
INSERT INTO sublist (ParentID, Data) VALUES (1, 2), (2, 3), (3, 6), (4, 8), (5, 4), (6, 5), (7, 1), (8, 9), (9, 11), (10, 4), (11, 6);

Answer 1

The simplest way of dealing with this is temporary tables, described here and here. If you create an empty table to store your results (let’s call it tbl_temp1) you can to this:

INSERT INTO tbl_temp1 (PingID, BaseID)
SELECT Ping.ID as PingID, Base.ID as BaseID 
FROM ...

Then you can query it however you like:

SELECT PingID, BaseID from tbl_temp1 ...

Edited to add:

From the docs for CREATE TEMPORARY TABLE:

You can use the TEMPORARY keyword when creating a table. A TEMPORARY
table is visible only to the current connection, and is dropped
automatically when the connection is closed. This means that two
different connections can use the same temporary table name without
conflicting with each other or with an existing non-TEMPORARY table of
the same name. (The existing table is hidden until the temporary table
is dropped.)