Try

    SELECT *
    FROM Table1
    INNER JOIN Table2 ON Table1.col LIKE CONCAT(&#39;%&#39;, Table2.col, &#39;%&#39;)

MySQL does string concatenation differently from other databases, so in case you want to port your app, you need to have an alternate version where &lt;code&gt;||&lt;/code&gt; is used as concatenation operator, as mentioned by Michael in another answer. This operator doesn&#39;t work in MySQL though, since it means &lt;code&gt;or&lt;/code&gt;.

How about this instead:

    SELECT * FROM Table1, Table2 WHERE Table1.col LIKE &#39;%&#39;+Table2.col+&#39;%&#39;;

Since you&#39;re selecting everything from both tables anyway, this would probably get you there.

    SELECT p.products_id, pd.products_name, p.products_model
    FROM products_description pd
    JOIN products p ON p.products_id = pd.products_id
    WHERE pd.products_name LIKE CONCAT( &#39;%&#39;, p.products_model, &#39;%&#39; )
    LIMIT 0 , 100

First off you have to restrict your request by (p.products_id = pd.products_id) and LIMIT. And look what time it took. After that you can go and make comparison with (WHERE). If you gonna compare directly within JOIN you will put down your db if there are at list 20 thousands items. Beware.)

Both of them emphasize text. The `&lt;em&gt;` tag shows text as italics, whereas `&lt;strong&gt;` makes it bold. Is this the only difference?

What is the difference between &lt;strong&gt; and &lt;em&gt; tags?

&gt; **Possible Duplicate:**  
&gt; [Perfomance of TypeCasting](https://stackoverflow.com/questions/1165602/perfomance-of-typecasting)  


How expensive is it to cast as object as a another object?

    CustomClass instance = GenericObject as CustomClass

Should it be avoided as all costs?

Wanting to see how others think about this. I&#39;m sure it&#39;s very situational.



How Expensive is Casting an Object?

I have been trying to get this working for quite a while now but it just doesn&#39;t seem to work, maybe it is is not even possible, what i am wanting to do is to perform a MySQL join query using like, such as this example i found...

    SELECT *
    FROM Table1
    INNER JOIN Table2 ON Table1.col LIKE &#39;%&#39; + Table2.col + &#39;%&#39;

but it just doesn&#39;t seem to work at all, any help that can be given would be brilliant, thanks !

MySQL join query using like?

I have been trying to get this working for quite a while now but it just doesn't seem to work, maybe it is is not even possible, what i am wanting to do is to perform a MySQL join query using like, such as this example i found...
<pre><code class="hljs language-sql">SELECT *
FROM Table1
INNER JOIN Table2 ON Table1.col LIKE '%' + Table2.col + '%'
</code></pre>
but it just doesn't seem to work at all, any help that can be given would be brilliant, thanks !

In MySQL, I&#39;m sick of adding the columns `dt_created` and `dt_modified` (which are date time stamps for creation and last modified respectively) to all the tables I have in my database.

Every time I `INSERT` or `UPDATE` the database, I will have to use the `NOW()` keyword. This is going all over my persistence. 

Is there any efficient alternative where MySQL can automatically store at least the datatime of the row that is inserted and let me retrieve it?

MySQL auto-store datetime for each row

I am trying to find some way to [relate column types][1] across the the most used Databases: [MySQL][2], [PostgreSQL][3], and [SQLite][4]. 

Here is what I have so far, but I&#39;m afraid it&#39;s not done and I need some people with more experience to help me finish any missing types.

    MySQL					PostgreSQL			SQLite
    
    TINYINT					SMALLINT			INTEGER
    SMALLINT				SMALLINT
    MEDIUMINT				INTEGER
    BIGINT					BIGINT
    BIT						BIT					INTEGER
    _______________________________________________________
    
    TINYINT UNSIGNED		SMALLINT			INTEGER
    SMALLINT UNSIGNED		INTEGER
    MEDIUMINT UNSIGNED		INTEGER
    INT UNSIGNED			BIGINT
    BIGINT UNSIGNED			NUMERIC(20)
    _______________________________________________________
    
    DOUBLE					DOUBLE PRECISION	REAL
    FLOAT					REAL				REAL
    DECIMAL					DECIMAL				REAL
    NUMERIC					NUMERIC				REAL
    _______________________________________________________
    
    BOOLEAN					BOOLEAN				INTEGER
    _______________________________________________________
    
    DATE					DATE				TEXT
    TIME					TIME
    DATETIME				TIMESTAMP
    _______________________________________________________
    
    TIMESTAMP DEFAULT 		TIMESTAMP DEFAULT	TEXT
    NOW()					NOW()	
    _______________________________________________________
    
    LONGTEXT				TEXT				TEXT
    MEDIUMTEXT				TEXT				TEXT
    BLOB					BYTEA				BLOB
    VARCHAR					VARCHAR				TEXT
    CHAR					CHAR				TEXT
    _______________________________________________________
    
    columnname INT			columnname SERIAL	INTEGER PRIMARY 
    AUTO_INCREMENT								KEY AUTOINCREMENT

  [1]: http://en.wikibooks.org/wiki/Converting_MySQL_to_PostgreSQL
  [2]: http://dev.mysql.com/doc/refman/5.1/en/data-types.html
  [3]: http://www.postgresql.org/docs/8.3/static/datatype.html
  [4]: http://www.sqlite.org/datatype3.html






Comparison of database column types in MySQL, PostgreSQL, and SQLite? (Cross-Mapping)

I worked on a PHP project earlier where prepared statements made the SELECT queries 20% faster.

I&#39;m wondering if it works on Python? I can&#39;t seem to find anything that specifically says it does or does NOT.



Does Python support MySQL prepared statements?

I have a MySQL table where rows are inserted dynamically.  Because I can not be certain of the length of strings and do not want them cut off, I make them varchar(200) which is generally much bigger than I need.  Is there a big performance hit in giving a varchar field much more length than necessary?

Importance of varchar length in MySQL table

How do I change the order of my table fields without deleting the field and re-inserting it, using PHP myAdmin?

PHP myAdmin - Change Field Order (Move Up Or Down)

I am trying to create a news page for a website I am working on. I decided that I want to use correct MySQL queries (meaning COUNT(id) and joins instead of more than one query or num_rows.) I&#39;m using a PDO wrapper, that should function fine, and this still fails when run directly through the MySQL CLI application.

Basically, I have 3 tables. One holds the news, one holds the comments and one holds the users. My aim here is to create a page which displays all (will paginate later) the news posts titles, bodies, authors and dates. This worked fine when I used a second query to get the username, but then I decided I&#39;d rather use a JOIN.

So what&#39;s the problem? Well, I need two joins. One is to get the author&#39;s username and the other to get the number of comments. When I simply go for the author&#39;s username, all works as expected. All the rows (there are 2) in the news table are displayed. However, when I added this second LEFT JOIN for the comments row, I end up only receiving one row from news (remember, there are 2,) and COUNT(comments.id) gives me 2 (it should display 1, as I have a comment for each post.)

What am I doing wrong? Why is it only displaying one news post, and saying that it has two comments, when there are two news posts, each with one comment?

    SELECT news.id, users.username, news.title, news.date, news.body, COUNT(comments.id)
    FROM news
    LEFT JOIN users
    ON news.user_id = users.id
    LEFT JOIN comments
    ON comments.news_id = news.id

Also, just to be sure about one other thing, my left join to comments is the correct way to get all posts regardless of whether they have comments or not, correct? Or would that be a right join? Oh, one last thing... if I switch comments.news_id = news.id to news.id = comments.news_id, I get 0 results.

MySQL Multiple Left Joins

Why does this work (returns &quot;one, two, three&quot;):

    var words = [&#39;one&#39;, &#39;two&#39;, &#39;three&#39;];
    $(&quot;#main&quot;).append(&#39;&lt;p&gt;&#39; + words.join(&quot;, &quot;) + &#39;&lt;/p&gt;&#39;);

and this work (returns &quot;the list: 111&quot;):

    var displayIt = function() {
        return &#39;the list: &#39; + arguments[0];
    }   
    $(&quot;#main&quot;).append(&#39;&lt;p&gt;&#39; + displayIt(&#39;111&#39;, &#39;222&#39;, &#39;333&#39;) + &#39;&lt;/p&gt;&#39;);

but not this (returns blank):

    var displayIt = function() {
        return &#39;the list: &#39; + arguments.join(&quot;,&quot;);
    }   
    $(&quot;#main&quot;).append(&#39;&lt;p&gt;&#39; + displayIt(&#39;111&#39;, &#39;222&#39;, &#39;333&#39;) + &#39;&lt;/p&gt;&#39;);

**What do I have to do to my &quot;arguments&quot; variable to be to use .join() on it?**



Why doesn&#39;t .join() work with function arguments?

Suppose I have a table of customers and a table of purchases. Each purchase belongs to one customer. I want to get a list of all customers along with their last purchase in one `SELECT` statement. What is the best practice? Any advice on building indexes?

Please use these table/column names in your answer:

 - customer: `id`, `name`
 - purchase: `id`, `customer_id`, `item_id`, `date`

And in more complicated situations, would it be (performance-wise) beneficial to denormalize the database by putting the last purchase into the customer table?

If the (purchase) `id` is guaranteed to be sorted by date, can the statements be simplified by using something like `LIMIT 1`?

SQL join: selecting the last records in a one-to-many relationship

How do you edit the attributes of a join model when using accepts_nested_attributes_for?

I have 3 models: Topics and Articles joined by Linkers

    class Topic &lt; ActiveRecord::Base
      has_many :linkers
      has_many :articles, :through =&gt; :linkers, :foreign_key =&gt; :article_id
      accepts_nested_attributes_for :articles
    end
    class Article &lt; ActiveRecord::Base
      has_many :linkers
      has_many :topics, :through =&gt; :linkers, :foreign_key =&gt; :topic_id
    end
    class Linker &lt; ActiveRecord::Base
      #this is the join model, has extra attributes like &quot;relevance&quot;
      belongs_to :topic
      belongs_to :article
    end
So when I build the article in the &quot;new&quot; action of the topics controller...

    @topic.articles.build
...and make the nested form in topics/new.html.erb...

    &lt;% form_for(@topic) do |topic_form| %&gt;
      ...fields...
      &lt;% topic_form.fields_for :articles do |article_form| %&gt;
        ...fields...

...Rails automatically creates the linker, which is great.
***Now for my question:*** My Linker model also has attributes that I want to be able to change via the &quot;new topic&quot; form. But the linker that Rails automatically creates has nil values for all its attributes except topic_id and article_id. How can I put fields for those other linker attributes into the &quot;new topic&quot; form so they don&#39;t come out nil?

Rails nested form with has_many :through, how to edit attributes of join model?

How do I perform the SQL Join equivalent in MongoDB?

For example say you have two collections (users and comments) and I want to pull all the comments with pid=444 along with the user info for each. 

    comments
      { uid:12345, pid:444, comment=&quot;blah&quot; }
      { uid:12345, pid:888, comment=&quot;asdf&quot; }
      { uid:99999, pid:444, comment=&quot;qwer&quot; }
   
    users
      { uid:12345, name:&quot;john&quot; }
      { uid:99999, name:&quot;mia&quot;  }


Is there a way to pull all the comments with a certain field (eg. ...find({pid:444}) ) and the user information associated with each comment in one go?

At the moment, I am first getting the comments which match my criteria, then figuring out all the uid&#39;s in that result set, getting the user objects, and merging them with the comment&#39;s results. Seems like I am doing it wrong. 

How do I perform the SQL Join equivalent in MongoDB?

I have a MySQL table for which I do very frequent `SELECT x, y, z FROM table WHERE x LIKE &#39;%text%&#39; OR y LIKE &#39;%text%&#39; OR z LIKE &#39;%text%&#39;` queries. Would any kind of index help speed things up?

There are a few million records in the table. If there is anything that would speed up the search, would it seriously impact disk usage by the database files and the speed of `INSERT` and `DELETE` statements? (no `UPDATE` is ever performed)

&lt;b&gt;Update&lt;/b&gt;: Quickly after posting, I have seen a lot of information and discussion about the way `LIKE` is used in the query; I would like to point out that the solution &lt;b&gt;must&lt;/b&gt; use `LIKE &#39;%text%&#39;` (that is, the text I am looking for is prepended and appended with a % wildcard). The database also has to be local, for many reasons, including security.

How to speed up SELECT .. LIKE queries in MySQL on multiple columns?

For whatever reason I have these classes called `.main_sub1`, `.main_sub2` etc. Never mind why I can&#39;t have `.main .sub`.

Is there a way with jQuery, sort of in the way it is possible to do with attributes, to get the classes containing `main`?

Element or class LIKE selector for jQuery?

I have mysql table that has a column that stores xml as a string. I need to find all tuples where the xml column contains a given string of 6 characters. Nothing else matters--all I need to know is if this 6 character string is there or not. 

So it probably doesn&#39;t matter that the text is formatted as xml.

Question: how can I search within mysql? 
ie 
`SELECT * FROM items WHERE items.xml [contains the text &#39;123456&#39;]`

Is there a way I can use the LIKE operator to do this?

Search for string within text column in MySQL

I looked around some and didn&#39;t find what I was after so here goes.

    SELECT * FROM trees WHERE trees.`title` LIKE  &#39;%elm%&#39;

This works fine, but not if the tree is named Elm or ELM etc...

How do I make SQL case insensitive for this wild-card search?

I&#39;m using MySQL 5 and Apache.

How can I search (case-insensitive) in a column using LIKE wildcard?

I want to query something with SQL&#39;s `like` query:

```SQL
SELECT * FROM users  WHERE name LIKE &#39;%m%&#39;
```

How can I achieve the same in MongoDB? I can&#39;t find an operator for `like` in [the documentation][1].

  [1]: http://www.mongodb.org/display/DOCS/Advanced+Queries


Content Type	Original Author	Original Content on Stackoverflow
Question	David	View Question on Stackoverflow
Solution 1 - Mysql	Tor Valamo	View Answer on Stackoverflow
Solution 2 - Mysql	brettkelly	View Answer on Stackoverflow
Solution 3 - Mysql	Александр Тарасов	View Answer on Stackoverflow

MySQL join query using like?

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

How Expensive is Casting an Object?

What is the difference between <strong> and <em> tags?

Attributions