Select Query Problems

WAMFT1 · October 16, 2015

Hi all, I am trying to create a query to pull all information from one table and just the last record for each prospect_id. I have been able to create the query in MSAccess (below) but cannot work out how to get this to work in php. Can someone please help? In access this works but to run on SQL it does not return any data.

The problem I believe lies around the LAST request.

SELECT DATABASE_Prospects.FirstName, DATABASE_Prospects.LastName, DATABASE_Prospects.State, DATABASE_Prospects.Active, DATABASE_Prospects.prospect_id, DATABASE_Prospects.dlr_group, DATABASE_Prospects.Income, DATABASE_Prospects.Probability, DATABASE_Prospects.added, Last(DATABASE_Prospect_Notes.comment) AS LastOfcomment
FROM DATABASE_Prospect_Notes RIGHT JOIN DATABASE_Prospects ON DATABASE_Prospect_Notes.prospect_id = DATABASE_Prospects.prospect_id
GROUP BY DATABASE_Prospects.FirstName, DATABASE_Prospects.LastName, DATABASE_Prospects.State, DATABASE_Prospects.Active, DATABASE_Prospects.prospect_id, DATABASE_Prospects.dlr_group, DATABASE_Prospects.Income, DATABASE_Prospects.Probability, DATABASE_Prospects.added
HAVING (((DATABASE_Prospects.Active)=1));

benanamen · October 16, 2015

Some Formatting would make it much more readable. Post an sql dump of your tables and data for us to test on. Mysql doesnt not have a "Last" function

SELECT database_prospects.firstname, 
       database_prospects.lastname, 
       database_prospects.state, 
       database_prospects.active, 
       database_prospects.prospect_id, 
       database_prospects.dlr_group, 
       database_prospects.income, 
       database_prospects.probability, 
       database_prospects.added, 
       Last(database_prospect_notes.comment) AS LastOfcomment 
FROM   database_prospect_notes 
       RIGHT JOIN database_prospects 
               ON database_prospect_notes.prospect_id = 
                  database_prospects.prospect_id 
GROUP  BY database_prospects.firstname, 
          database_prospects.lastname, 
          database_prospects.state, 
          database_prospects.active, 
          database_prospects.prospect_id, 
          database_prospects.dlr_group, 
          database_prospects.income, 
          database_prospects.probability, 
          database_prospects.added 
HAVING (( ( database_prospects.active ) = 1 ))

Edited October 16, 2015 by benanamen

WAMFT1 · October 16, 2015

Attached is a link to the SQL dump, thanks for your help. Hopefully there will be a work around.

http://www.wamft.com.au/prospects.sql

benanamen · October 16, 2015

Here is the MySQL version to get you up and running. You should always use lowercase column names. You have some all lower, some upper and lower

SQL

SET FOREIGN_KEY_CHECKS=0;

-- ----------------------------
-- Table structure for database_prospect_notes
-- ----------------------------
DROP TABLE IF EXISTS `database_prospect_notes`;
CREATE TABLE `database_prospect_notes` (
  `note_id` int(11) NOT NULL AUTO_INCREMENT,
  `prospect_id` int(11) NOT NULL,
  `staff_id` int(11) NOT NULL,
  `comment` mediumtext NOT NULL,
  `date` datetime NOT NULL,
  PRIMARY KEY (`note_id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of database_prospect_notes
-- ----------------------------
INSERT INTO `database_prospect_notes` VALUES ('1', '1', '1', 'Police check uncovered issues?', '2015-10-15 12:02:33');
INSERT INTO `database_prospect_notes` VALUES ('2', '1', '236', 'Appointed', '2015-10-15 14:29:27');

-- ----------------------------
-- Table structure for database_prospects
-- ----------------------------
DROP TABLE IF EXISTS `database_prospects`;
CREATE TABLE `database_prospects` (
  `prospect_id` int(11) NOT NULL AUTO_INCREMENT,
  `FirstName` varchar(20) NOT NULL,
  `LastName` varchar(20) NOT NULL,
  `State` varchar(3) NOT NULL,
  `Active` int(1) NOT NULL,
  `Email` varchar(100) NOT NULL,
  `UserType` varchar( NOT NULL DEFAULT 'Prospect',
  `dlr_group` varchar(10) NOT NULL,
  `middlename` varchar(30) NOT NULL,
  `carname` varchar(80) NOT NULL,
  `tradingname` varchar(80) NOT NULL,
  `arn` int(6) NOT NULL,
  `carn` int(6) NOT NULL,
  `authorisations` varchar(20) NOT NULL,
  `phonehome` varchar(15) NOT NULL,
  `phonework` varchar(15) NOT NULL,
  `phonemobile` varchar(15) NOT NULL,
  `faxwork` varchar(15) NOT NULL,
  `website` varchar(80) NOT NULL,
  `paddress` varchar(50) NOT NULL,
  `psuburb` varchar(30) NOT NULL,
  `pstate` varchar(3) NOT NULL,
  `ppostcode` varchar(4) NOT NULL,
  `haddress` varchar(50) NOT NULL,
  `hsuburb` varchar(30)  NOT NULL,
  `hstate` varchar(3)  NOT NULL,
  `hpostcode` varchar(4)  NOT NULL,
  `baddress` varchar(50)  NOT NULL,
  `bsuburb` varchar(30)  NOT NULL,
  `bstate` varchar(3) NOT NULL,
  `bpostcode` varchar(4) NOT NULL,
  `raddress` varchar(50) NOT NULL,
  `rsuburb` varchar(30)  NOT NULL,
  `rstate` varchar(3)  NOT NULL,
  `rpostcode` varchar(4)  NOT NULL,
  `dob` date DEFAULT NULL,
  `placeofbirth` varchar(50)  NOT NULL,
  `split` varchar(20)  NOT NULL,
  `abn` varchar(15)  NOT NULL,
  `exdealer` varchar(40)  NOT NULL,
  `software` varchar(30) NOT NULL,
  `softwaremodules` varchar(30)  NOT NULL,
  `research` varchar(30)  NOT NULL,
  `Income` varchar(20)  NOT NULL,
  `Probability` varchar(4)  NOT NULL,
  `Cashflow` varchar(20) NOT NULL,
  `added` date NOT NULL,
  PRIMARY KEY (`prospect_id`),
  KEY `id_2` (`prospect_id`),
  KEY `id` (`prospect_id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of database_prospects
-- ----------------------------
INSERT INTO `database_prospects` VALUES ('1', 'Smith', 'John', 'NSW', '1', '', 'Prospect', '--', '', 'John Smith', '', '0', '0', '--', '', '', '', '', '', '', '', '--', '', '', '', '--', '', '', '', '--', '', '', '', '--', '', '0000-00-00', '', '', '', '', '', '', '', '$15,000', '100%', '15,000', '2015-10-15');

Query to get some data

SELECT d.firstname,
       d.lastname,
       d.state,
       d.active,
       d.prospect_id,
       d.dlr_group,
       d.income,
       d.probability,
       d.added,
       n.comment AS LastOfcomment
FROM
database_prospect_notes AS n
LEFT JOIN database_prospects AS d ON n.prospect_id= d.prospect_id
WHERE d.active=1
ORDER BY n.note_id DESC LIMIT 1

Edited October 16, 2015 by benanamen

WAMFT1 · October 16, 2015

Excellent, this partially working, are you able to assist a little further?

The above pulls through the last note but I need it to pull the last note for each prospect_id in database_prospects.

Effectively all records from database_prospects and the last record for each from database_prospect_notes. Hopefully this makes sense?

mac_gyver · October 16, 2015

see this link - http://dev.mysql.com/doc/refman/5.6/en/example-maximum-column-group-row.html where what you are doing is getting the maximum note id per group.

using the last method shown at that link (left join) the following works (cannot vouch for how efficient it is, but it is fairly easy to understand or modify to use any JOINed table query for the two sub-queries) -

SELECT t1.* FROM
(SELECT p.*, n.note_id, n.comment FROM prospects p LEFT JOIN notes n ON p.id = n.prospect_id) t1
 LEFT JOIN
(SELECT p.id, n.note_id FROM prospects p LEFT JOIN notes n ON p.id = n.prospect_id) t2
 ON t1.id = t2.id
 AND t1.note_id < t2.note_id
 WHERE t2.id IS NULL;

this is using simplified table naming with - a `prospects` table with at least an `id` column and a `notes` table with at least `note_id`, `prospect_id`, and `comment` columns.

WAMFT1 · October 16, 2015

I am dumb as here... I am completely lost. I thought that this would be a simple exercise.

I am back to square 1 now with nothing coming up at all. I don't understand what is going on.

mac_gyver · October 16, 2015

a) are you running the query directly against your database using a query browser of some kind so that you would be seeing any errors from the query?

b) what i posted isn't a copy/paste query. you need to adapt it to use your table and column names. you would also need to add in the active=1 logic.

Barand · October 16, 2015

The above pulls through the last note but I need it to pull the last note for each prospect_id in database_prospects.

In that case, the test data you provided, with a single prospect, is not fit for purpose

WAMFT1 · October 16, 2015

If it helps Barand, I have added some more sample data. http://www.wamft.com.au/prospects.sql

I am still pulling my hair out here, this is just too complicated for my simple brain to comprehend. I am not a very advance coder.

Barand · October 16, 2015

My data

mysql> SELECT * FROM database_prospects;
+-------------+-----------+----------+--------+
| prospect_id | FirstName | LastName | Active |
+-------------+-----------+----------+--------+
|           1 | John      | Smith    |      1 |
|           2 | Jane      | Doe      |      0 |
|           3 | Joe       | Bloggs   |      1 |
|           4 | Davy      | Jones    |      1 |
+-------------+-----------+----------+--------+
4 rows in set (0.00 sec)

mysql> SELECT * FROM database_prospect_notes;
+---------+-------------+----------+-----------+---------------------+
| note_id | prospect_id | staff_id | comment   | date                |
+---------+-------------+----------+-----------+---------------------+
|       1 |           1 |      123 | comment 1 | 2015-07-12 00:00:00 |
|       2 |           1 |      120 | comment 2 | 2015-09-14 00:00:00 |
|       3 |           2 |      125 | comment 3 | 2015-06-22 00:00:00 |
|       4 |           2 |      128 | comment 4 | 2015-09-01 00:00:00 |
|       5 |           3 |      125 | comment 5 | 2015-08-02 00:00:00 |
|       6 |           3 |      129 | comment 6 | 2015-09-05 00:00:00 |
+---------+-------------+----------+-----------+---------------------+
6 rows in set (0.00 sec)

Query

SELECT
    p.prospect_id
  , p.FirstName
  , p.LastName
  , notes.staff_id
  , notes.comment
  , notes.date
FROM database_prospects p
	LEFT join
		(
        -- 
        -- subquery to get notes record with latest date
        -- 
        SELECT n.prospect_id
          , n.staff_id
          , n.date
          , n.comment
	FROM
        database_prospect_notes n 
	INNER JOIN
	   (
            -- 
            -- subquery to find latest dates
            -- 
			SELECT prospect_id
				, MAX(date) as date
			FROM database_prospect_notes
			GROUP BY prospect_id
	    ) latest ON n.prospect_id = latest.prospect_id
			AND n.date = latest.date
) notes USING (prospect_id)
WHERE p.active = 1;

Results

+-------------+-----------+----------+----------+-----------+---------------------+
| prospect_id | FirstName | LastName | staff_id | comment   | date                |
+-------------+-----------+----------+----------+-----------+---------------------+
|           1 | John      | Smith    |      120 | comment 2 | 2015-09-14 00:00:00 |
|           3 | Joe       | Bloggs   |      129 | comment 6 | 2015-09-05 00:00:00 |
|           4 | Davy      | Jones    |     NULL | NULL      | NULL                |
+-------------+-----------+----------+----------+-----------+---------------------+

WAMFT1 · October 16, 2015

Barand, You are awesome.

Works exactly how I need it to. How much do I owe you. I have spent 3 days trying to work this out.

Barand · October 16, 2015

Are you prepared to remortgage your house?

benanamen · October 17, 2015

Sub-query's can take a toll on your database. One thing to point out about @Barands solution is that since it is based on datetime rather than the actual last record inserted per prospect, if there are two records with the same exact date-time for a given prospect, you are going to get more than one result for that prospect. Per your specs, you just wanted one result per prospect only and that being the LAST record.

Here is an example how to do it that will not take a sub-query toll on the DB and will give you the actual last record inserted per prospect and is a lot less code.

* I didn't see that you were trying to get the staff_id or the comment date so I left it out.

SELECT p.*, 
       Substring_index(Group_concat(n.`comment` ORDER BY n.note_id DESC), ',', 1 ) AS last_comment
FROM   database_prospects AS p 
       INNER JOIN database_prospect_notes AS n ON p.prospect_id = n.prospect_id 
WHERE  p.active = 1 
GROUP  BY p.prospect_id

Edited October 17, 2015 by benanamen

Barand · October 17, 2015

It's actually a datetime field in the original database

CREATE TABLE IF NOT EXISTS `DATABASE_Prospect_Notes` (
  `note_id` int(11) NOT NULL AUTO_INCREMENT,
  `prospect_id` int(11) NOT NULL,
  `staff_id` int(11) NOT NULL,
  `comment` mediumtext NOT NULL,
  `date` datetime NOT NULL,
  PRIMARY KEY (`note_id`)
)

[edit] PS. Using GROUP_CONCAT() can result in silent truncation when the result is > 1024 characters. As these are TEXT fields the last one may not be complete in the list.

If I take out the requirement to show those with no comments (original used right join) then the query shrinks

SELECT
   p.prospect_id
 , p.FirstName
 , p.LastName
 , n.staff_id
 , n.comment
 , n.date
FROM database_prospects p
	INNER join
	database_prospect_notes n ON p.prospect_id = n.prospect_id
	INNER JOIN
		(
		SELECT prospect_id
			, MAX(date) as date
		FROM database_prospect_notes
		GROUP BY prospect_id
		) latest ON n.prospect_id = latest.prospect_id
				AND n.date = latest.date
WHERE p.active = 1;

Edited October 17, 2015 by Barand

benanamen · October 17, 2015

Yes barand, the default setting is 1024 and it will truncate at that point. But, it is a setting and it can be changed. Much like the default upload size in PHP is two meg but you usually want to always change that. Just a part of performance tuning. I don't expect newbies to know about it let alone how do it. I am sure you would agree to avoid sub queries when possible.

A bit confused why you point out about the original database having a datetime column. The db that you and I both used also has a datetime. The only difference is I didnt use date time to find the last record which as I pointed out will not work if there are two records with the same date time for a given prospect.

Edited October 17, 2015 by benanamen

Barand · October 17, 2015

I would agree to avoid dependent subqueries.

As for ids, I take the view that, for the most part, they are internal linking fields and that an application should work equally well if unique ids were allocated randomly or sequentially.

benanamen · October 17, 2015

Ok, confused again. I agree with the unique id's, but we were not talking about unique id's. (Where we?)

Barand · October 17, 2015

If we weren't, then what was to stop two comments having the same id?

benanamen · October 17, 2015

Ok, really confused now. There are unique id's, the note_id. The page I am on is where I asked you about mentioning the date-time and you started talking about unique ids.

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