You can&#39;t have a UNIQUE index on a text column in MySQL.

If you want to index on a TEXT or a BLOB field, you must specify a fixed length to do that.

From MySQL [documentation][1]:

&gt; BLOB and TEXT columns also can be
&gt; indexed, but a prefix length must be
&gt; given.

Example:

    CREATE UNIQUE INDEX index_name ON misc_info (key(10));

  [1]: http://dev.mysql.com/doc/refman/5.0/en/create-index.html

Two things:

 1. Key is a reserved word. 
 2. You have to specify a length for a `UNIQUE(key) TEXT value`.

I think it chokes on the `key` field name rather than the TEXT type (which should be perfectly fine). 

[Reserved Words in mySQL][1]



(And as @Pablo already said, memo fields can&#39;t be unique.)


  [1]: http://dev.mysql.com/doc/refman/5.1/en/reserved-words.html

I&#39;m trying to make ajax file upload . I read that it is not possible to do that without using `iframe` .   
I wrote :

    &lt;iframe id=&quot;uploadTrg&quot; name=&quot;uploadTrg&quot; height=&quot;0&quot; width=&quot;0&quot; frameborder=&quot;0&quot; scrolling=&quot;yes&quot;&gt;&lt;/iframe&gt;
    &lt;form id=&quot;myForm&quot; action=&quot;file-component&quot; method=&quot;post&quot; enctype=&quot;multipart/form-data&quot;  target=&quot;uploadTrg&quot;&gt;
    File: &lt;input type=&quot;file&quot; name=&quot;file&quot;&gt;
    &lt;input type=&quot;submit&quot; value=&quot;Submit&quot; id=&quot;submitBtn&quot;/&gt;
    &lt;/form&gt;

and using jquery form plugin : 

    $(&#39;#myForm&#39;).ajaxForm({
        dataType:  &#39;json&#39;,
        success:   function(data){
            alert(data.toSource());
        }
    });

**The Result :**  

the file is uploaded successfully and I can see the uploaded file , but a dialog box appears :  

![alt text][1]  


since I send back a json result to display the file name + size etc ..

**My Question :**
How can I use the iFrame to be able to make &quot; ajax file upload&quot;.

Note:


 1. I don&#39;t prefer to use special plugin to upload file , if there is more appropriate/easier  solutions.
 2. I use jsp/servlets as a server-side language .. but I think it does not make sense which language I use .

Thanks

  [1]: https://farm5.static.flickr.com/4065/4640629084_0842838e5f_o.png

How to make Asynchronous(AJAX) File Upload using iframe?

Is it possible to migrate from TFS 2008 to Git, and still preserve all the history, etc?
I&#39;ve seen some references that talk about doing it through SVN, but that seems rather complicated, and complicates my mission to introduce Git at my job.

Migrating from TFS to Git

I ran this using MySql and it appears to not like `TEXT`. With SQL server I use `nvarchar(max)` What should I use in MySql? In other tables some fields will be descriptions and may be long so at the moment I am thinking that fixed length is bad.

    create table if not exists 
        misc_info (
            id INTEGER PRIMARY KEY AUTO_INCREMENT NOT NULL,
            key TEXT UNIQUE NOT NULL,
            value TEXT NOT NULL
        )ENGINE=INNODB;



Indexing a MySql TEXT column?

I ran this using MySql and it appears to not like <code>TEXT</code>. With SQL server I use <code>nvarchar(max)</code> What should I use in MySql? In other tables some fields will be descriptions and may be long so at the moment I am thinking that fixed length is bad.
<pre><code class="hljs language-sql">create table if not exists 
 misc_info (
 id INTEGER PRIMARY KEY AUTO_INCREMENT NOT NULL,
 key TEXT UNIQUE NOT NULL,
 value TEXT NOT NULL
 )ENGINE=INNODB;
</code></pre>

I am generating tables from classes in .NET and one problem is a class may have a field name `key` which is a reserved MySQL keyword. How do I escape it in a create table statement? (Note: The other problem below is text must be a fixed size to be indexed/unique)

    create table if not exists misc_info (
    id INTEGER PRIMARY KEY AUTO_INCREMENT NOT NULL,
    key TEXT UNIQUE NOT NULL,
    value TEXT NOT NULL)ENGINE=INNODB;



How do I escape reserved words used as column names? MySQL/Create Table

Could someone tell me how to add a new line in a text that I enter in a MySql table?

I tried using the `&#39;\n&#39;` in the line I entered with `INSERT INTO` statement but `&#39;\n&#39;` is shown as it is.

Actually I have created a table in MS Access with some data. MS Access adds new line with `&#39;\n&#39;`.  I am converting MS Access table data into MySql . But when I convert, the `&#39;\n&#39;` is ignored and all the text is shown in one single line when I display it from MySql table on a PHP form.

Can anyone tell me how MySQL can add a new line in a text? Awaiting response, thanks!!

Adding a line break in MySQL INSERT INTO text

Why do you need to place columns you create yourself (for example `select 1 as &quot;number&quot;`) after `HAVING` and not `WHERE` in MySQL?

And are there any downsides instead of doing `WHERE 1` (writing the whole definition instead of a column name)?

WHERE vs HAVING

I want to use foreign keys to keep the integrity and avoid orphans (I already use innoDB).

How do I make a SQL statment that DELETE ON CASCADE?

If I delete a category then how do I make sure that it would not delete products that also are related to other categories.

The pivot table &quot;categories_products&quot; creates a many-to-many relationship between the two other tables.

    categories
    - id (INT)
    - name (VARCHAR 255)
    
    products
    - id
    - name
    - price
    
    categories_products
    - categories_id
    - products_id




MySQL foreign key constraints, cascade delete

How can I undo the most recently executed mysql query?

How can I undo a mysql statement that I just executed?

What is an index in SQL?

I&#39;ve got a very large MySQL table with about 150,000 rows of data. Currently, when I try and run

    SELECT * FROM table WHERE id = &#39;1&#39;;

the code runs fine as the ID field is the primary index.
However, for a recent development in the project, I have to search the database by another field. For example:

    SELECT * FROM table WHERE product_id = &#39;1&#39;;

This field was not previously indexed; however, I&#39;ve added one, so mysql now indexes the field, but when I try to run the above query, it runs very slowly. An EXPLAIN query reveals that there is no index for the product_id field when I&#39;ve already added one, and as a result the query takes any where from 20 minutes to 30 minutes to return a single row.

My full EXPLAIN results are:

    | id | select_type | table | type | possible_keys| key  | key_len | ref  | rows  | Extra       |
    +----+-------------+-------+------+--------------+------+---------+------+-------+------------------+
    |  1 | SIMPLE      | table | ALL  | NULL         | NULL | NULL    | NULL |157211 | Using where |
    +----+-------------+-------+------+--------------+------+---------+------+-------+------------------+

It might be helpful to note that I&#39;ve just taken a look, and ID field is stored as INT whereas the PRODUCT_ID field is stored as VARCHAR. Could this be the source of the problem?

How do I add indexes to MySQL tables?

I&#39;ve been using indexes on my MySQL databases for a while now but never properly *learnt* about them. Generally I put an index on any fields that I will be searching or selecting using a `WHERE` clause but sometimes it doesn&#39;t seem so black and white.

**What are the best practices for MySQL indexes?**

Example situations/dilemmas:

* If a table has six columns and all of them are searchable, should I index all of them or none of them?

* What are the negative performance impacts of indexing?

* If I have a VARCHAR 2500 column which is searchable from parts of my site, should I index it?



MySQL indexes - what are the best practices?

Is there any way I can get the actual row number from a query?

I want to be able to order a table called league_girl by a field called score; and return the username and the actual row position of that username.

I&#39;m wanting to rank the users so i can tell where a particular user is, ie. Joe is position 100 out of 200, i.e.

    User Score Row
    Joe  100    1
    Bob  50     2
    Bill 10     3


I&#39;ve seen a few solutions on here but I&#39;ve tried most of them and none of them actually return the row number.

I have tried this:

    SELECT position, username, score
    FROM (SELECT @row := @row + 1 AS position, username, score 
           FROM league_girl GROUP BY username ORDER BY score DESC) 

As derived 

...but it doesn&#39;t seem to return the row position.

Any ideas?


With MySQL, how can I generate a column containing the record index in a table?

The team I&#39;m working with decided to create a table with a varchar primary key. This table is referenced by another table on this primary key.

I&#39;ve the habit to create an integer primary key, following what I learnt at university. I&#39;ve read that there is a performance boost using integer primary key.

The matter is that I don&#39;t know any other reason for creating an integer primary key. Do you have any tips?

Content Type	Original Author	Original Content on Stackoverflow
Question	user34537	View Question on Stackoverflow
Solution 1 - Mysql	Pablo Santa Cruz	View Answer on Stackoverflow
Solution 2 - Mysql	khai_khai	View Answer on Stackoverflow
Solution 3 - Mysql	Pekka	View Answer on Stackoverflow

Indexing a MySql TEXT column?

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

Migrating from TFS to Git

How to make Asynchronous(AJAX) File Upload using iframe?

Attributions