create table statement with indexes

@rgb192: you can post your questions in more than one Zone.  For example, you can post questions like this in both the PHP and MySQL Zones.

After the table is created (and if possible, after the table is loaded) you can use something like this:

$mysqli->query("ALTER TABLE `a_messages2` ADD INDEX ( `profile_id` )" );

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so are you saying I can just add index to every column and this will reduce select times

so what is the command to add index to all columns

ALTER TABLE `a_messages2` ADD INDEX ( `a_messages_id`,`profile_id`, `sender`, `message_id`, `this_user` )

add index to all columns

This is an ambiguous question. Let me try to explain why.

You can have an index on a single column.  You can have an individual index on each of several columns.  You can also have an index that spans two or more columns, or even the entire table, taking all columns into account simultaneously.  So would it be better to have one index that covers all of the columns at once?  Or should you have one index for each column?  The choice of the exact kind of index you need is something that will be dependent on the queries you expect to optimize.  You may want to write these queries and use EXPLAIN SELECT to see what the SQL engine is doing with your queries.  Then you will know what kinds of indexes will be best

explain
                      SELECT
                      profile_id,this_user
                      FROM a_messages2
                      WHERE (
                               ( /* here we determine who originated the profile */
                                   message_id IN (SELECT min(message_id)
                                                  FROM a_messages2 GROUP BY profile_id)
                                AND
                                   profile_id <> sender /* originated by staff */
                               )
                            OR
                               ( /* here we determine who has sent latest message */
                                   message_id IN (SELECT max(message_id)
                                                  FROM a_messages2 GROUP BY profile_id)
                                AND
                                   profile_id = sender /* needs a response by staff */
                               )
                            )
                      GROUP BY profile_id
                      HAVING count(*) = 2

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and these are results

id,select_type,table,type,possible_keys,key,key_len,ref,rows,Extra
1,PRIMARY,a_messages2,ALL,NULL,NULL,NULL,NULL,9707,"Using where; Using temporary; Using filesort"
3,"DEPENDENT SUBQUERY",a_messages2,ALL,NULL,NULL,NULL,NULL,9707,"Using temporary; Using filesort"
2,"DEPENDENT SUBQUERY",a_messages2,ALL,NULL,NULL,NULL,NULL,9707,"Using temporary; Using filesort"

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What is the point for this query?

Presumably you have one table (working) where questions are open and are being actively monitored. here you need only look whether staff needs to respond.
When the user is satisfied with the response they received, they would presumably close the issue as resolved at which point the issue will be moved to an archive table and out of the working table.

Similarly for the staff originated question, when the user has responded adequately, the question is closed and moved out of this queue.

skullnobrains:

you're hiding some information : there is a primary key and it is actually used. i'd assume that it is similar to the compound index i was suggesting

yes there is a unique key

CREATE TABLE `a_messages2` (
  `a_messages_id` int(11) NOT NULL auto_increment,
  `conversation_id` bigint(20) default NULL,
  `profile_id` varchar(20) default NULL,
  `sender` varchar(20) default NULL,
  `message_id` bigint(20) default NULL,
  `message_text` varchar(1000) default NULL,
  `dateAgo` varchar(20) default NULL,
  `message_read` tinyint(4) default NULL,
  `this_user` varchar(20) default NULL,
  PRIMARY KEY  (`a_messages_id`),
  UNIQUE KEY `unique_message_id` (`message_id`)
) ENGINE=MyISAM AUTO_INCREMENT=9969 DEFAULT CHARSET=utf8;

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select profile_id,this_user
FROM
a_messages2
WHERE
profile_id = sender /* needs a response by staff */
and message_id IN
      (
      SELECT
      max(message_id)
      FROM
      a_messages2
      WHERE
      profile_id IN
            (
            SELECT
            profile_id
            FROM a_messages2
            WHERE
            message_id IN (SELECT min(message_id) FROM a_messages2 GROUP BY profile_id)
            AND profile_id <> sender /* originated by staff */
            )
      GROUP BY profile_id
      )

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I ran your query and it takes a long time to run (which is similar to the original query that was made for me
should I run explain select on your query or will you edit now that you know of unique key?

arnold:

What is the point for this query?

I think the boss needs this for reporting

(profile_id,message_id) will likely be much more usefull as mysql will be able to retrieve the min message_ids for each profile_id very fast, while it currently requires a full table scan, a temporary table and a sort

I think I agree but I do not fully understand the query because I did not write the query
So how would you change the query.

I do not understand the other data you wrote

modifying skullnobrains code
https://www.experts-exchange.com/questions/28318003/create-table-statement-with-indexes.html?anchorAnswerId=39726770#a39726770

CREATE TABLE `a_messages3` (
       `a_messages_id` INT (11) auto_increment  primary key
     , `profile_id` VARCHAR(20)
     , `sender` VARCHAR(20)
     , `message_id` BIGINT (20)
     , `this_user` VARCHAR(20)
     , PRIMARY KEY messages_id
     , INDEX profile_id (profile_id)
     , INDEX profile_id_and_message_id (profile_id,message_id)
     );

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Error Code: 1064. You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ' INDEX profile_id (profile_id)      , INDEX profile_id_and_message_id (profile_i' at line 8

i forgot a couple of brackets
PRIMARY KEY messages_id --> PRIMARY KEY (messages_id)

sorry for the typo, but on the other hand, i would assume you could debug that much by reading the manual http://dev.mysql.com/doc/refman/5.1/en/create-table.html

CREATE TABLE `a_messages3` (
       `a_messages_id` INT (11) auto_increment  primary key
     , `profile_id` VARCHAR(20)
     , `sender` VARCHAR(20)
     , `message_id` BIGINT (20)
     , `this_user` VARCHAR(20)
     , PRIMARY KEY (a_messages_id)
     , INDEX profile_id (profile_id)
     , INDEX profile_id_and_message_id (profile_id,message_id)
     );


Error Code: 1068. Multiple primary key defined


but this worked



CREATE TABLE `a_messages3` (
       `a_messages_id` INT (11) auto_increment
     , `profile_id` VARCHAR(20)
     , `sender` VARCHAR(20)
     , `message_id` BIGINT (20)
     , `this_user` VARCHAR(20)
     , PRIMARY KEY (a_messages_id)
     , INDEX profile_id (profile_id)
     , INDEX profile_id_and_message_id (profile_id,message_id)
     );


is this correct?

note: a_messages_id is just a primary key column with no data other than an auto increment number

message_id is a big int of the message which is an important value

yes. there are 2 ways to define primary keys and you're not supposed to use both at the same time. either would be fine, i just forgot to remove one.

i hardly understand why you ask since you obviously figured it out.

---

btw, if you're not using the primary key, you're not required to have one. when using myisam tables, defining a useless PK is a loss of space and write performance. when using innodb, it won't make a difference since innodb would create a hidden auto-increment column and use it as the primary key if you don't declare one.

other than that, if a column such as message_id is unique, most likely it should be declared as the primary key.

---

did you do any tests ?

I changed a_messages2 to a_messages3

a_messages3 has only needed columns

CREATE TABLE `a_messages3` (
  `a_messages_id` int(11) NOT NULL auto_increment,
  `profile_id` varchar(20) default NULL,
  `sender` varchar(20) default NULL,
  `message_id` bigint(20) default NULL,
  `this_user` varchar(20) default NULL,
  PRIMARY KEY  (`a_messages_id`),
  KEY `profile_id` (`profile_id`),
  KEY `profile_id_and_message_id` (`profile_id`,`message_id`)
) ENGINE=MyISAM AUTO_INCREMENT=9708 DEFAULT CHARSET=utf8;

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select profile_id,this_user
FROM
a_messages3
WHERE
profile_id = sender /* needs a response by staff */
and message_id IN
      (
      SELECT
      max(message_id)
      FROM
      a_messages3
      WHERE
      profile_id IN
            (
            SELECT
            profile_id
            FROM a_messages3
            WHERE
            message_id IN (SELECT min(message_id) FROM a_messages3 GROUP BY profile_id)
            AND profile_id <> sender /* originated by staff */
            )
      GROUP BY profile_id
      )

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Error Code: 1317 Query execution was interrupted


problem is query still will not run in under 10 minutes

I need to extend 10 minutes and delete all other users than staff1 (I still did not do command delete from a_messages where this_user!='staff1') just to run the query which is the same problem i had previously

So is the query working better? I am not sure because I have difficulty with new and previous queries.

I do not fully understand yet, so I will need to do database tutorials.  Queries work but I do not understand why slow.  I need to learn more about indexes and mysql reporting.

thanks for the correct direction.