Several ways:

    # Comment
    -- Comment
    /* Comment */

Remember to [put the space after `--`][1].

See [the documentation][2].

  [1]: https://stackoverflow.com/questions/14435989/mysql-is-not-supporting-single-line-comments-here-what-would-be-the-reason
  [2]: http://dev.mysql.com/doc/refman/5.1/en/comments.html



&quot;A comment for a column can be specified with the `COMMENT` option. The comment is displayed by the `SHOW CREATE TABLE` and `SHOW FULL COLUMNS` statements. This option is operational as of MySQL 4.1. (It is allowed but ignored in earlier versions.)&quot;

As an example

    --
    -- Table structure for table &#39;accesslog&#39;
    --

    CREATE TABLE accesslog (
    aid int(10) NOT NULL auto_increment COMMENT &#39;unique ID for each access entry&#39;, 
    title varchar(255) default NULL COMMENT &#39;the title of the page being accessed&#39;,
    path varchar(255) default NULL COMMENT &#39;the local path of teh page being accessed&#39;,
    ....
    ) TYPE=MyISAM;

You can use single-line comments:

```lang-none
-- this is a comment
# this is also a comment
```

Or a multiline comment:

```lang-none
/*
   multiline
   comment
*/
```


From [here][1] you can use:

```lang-none
#  For single line comments
-- Also for single line, must be followed by space/control character
/*
    C-style multiline comment
*/
```

  [1]: http://dev.mysql.com/doc/refman/5.1/en/comments.html


```lang-sql
/* comment here */
```

Here is an example: 

```lang-sql
SELECT 1 /* this is an in-line comment */ + 1;
```

Reference: *[9.7 Comments][1]* 

  [1]: http://dev.mysql.com/doc/refman/5.0/en/comments.html



Three types of commenting are supported:

 1. Hash base single line commenting using #

        Select * from users ; # this will list users

 2. Double Dash commenting using `--`

        Select * from users ; -- this will list users

    Note: It&#39;s important to have single white space just after `--`

 3. Multi line commenting using /* */

        Select * from users ; /* this will list users */





Instead of supporting method overloading Ruby overwrites existing methods. Can anyone explain why the language was designed this way?

Why doesn&#39;t ruby support method overloading?

I was wondering if it is possible to check if `mod_rewrite` is enabled on **Apache** AND **IIS** in **`PHP`**.

**ModRewrite** for IIS exists. Check it [`here`][1].

So, I&#39;m looking for a PHP script that checks for `mod_rewrite` on **Apache** and **IIS.**

Does anyone know such script or can write one?

Especially for Microsoft **IIS**.

Thanks!

  [1]: http://www.micronovae.com/ModRewrite/ModRewrite.html

How to check if mod_rewrite is enabled in php?

I want to add comment in SQL code. How can I do this? I&#39;m using MySQL.

How can I add comments in MySQL?

<p>I want to add comment in SQL code. How can I do this? I'm using MySQL.</p>


The field `table`.`name` contains &#39;Stylus Photo 2100&#39; and with the following query

    SELECT `name` FROM `table` WHERE `name` LIKE &#39;%Stylus 2100%&#39;

I get no results. Of course i would if i searched

    SELECT `name` FROM `table` WHERE `name` LIKE &#39;%Photo 2100%&#39;

How can I select the record by searching &#39;Stylus 2100&#39; ?

Thanks 

MySQL SELECT LIKE or REGEXP to match multiple words in one record

I have a column in my mySQL DB that has some rows. One of this row is a DATE, like this: `2012-02-01`

What I want to achieve is to do a SELECT with PHP based only on the year and month.

The logic of the SELECT will be the following:

    $q=&quot;SELECT * FROM projects WHERE Date=&quot;SELECT HERE THE SPECIFIC YEAR AND MONTH&quot;&quot;;

The specific month and year will be be passed from a `$_POST` variable, like this `$_POST[&#39;period&#39;]=&quot;2012-02&quot;;`

How can I do it?

Select mySQL based only on month and year

The following works - returns Y when chargeback equal to 1 else it defaults to N

    IF(fd.charge_back = 1, &#39;Y&#39;, &#39;N&#39;) AS charge_back

however I cannot seem to get this one working?  Is the syntax valid

    IF(compliment = (&#39;set&#39; OR &#39;Y&#39; OR 1), &#39;Y&#39;, &#39;N&#39;) AS customer_compliment



mysql SELECT IF statement with OR

I&#39;m writing a PHP application that will store `STUDENT` data in a MySQL relational database. I&#39;m trying to find the best way / datatype to store a month and year together without the day.

I don&#39;t know whether I should just store it as a DATE and use PHP someway to just store the day as the 1-st or use a different datatype that I&#39;m not currently familiar with. Ideally, I do not want to store a day, because the day will not always be the same and would require changing PHP source code if the day changed in the future.

Just for more background info, I&#39;m storing a STUDENT&#39;s `INTENT_TO_GRAD`. The client seems to only want this information as a reference or a visual for a report as opposed to using it for data manipulation. In other words, the only functional requirement for this data is to be displayed in a report.

MySQL datatype to store month and year only

In MySQL I am trying to copy a row with an **autoincrement** `column ID=1` and **insert** the data into same table as a new row with `column ID=2`.

How can I do this in a single query?

How to copy a row and insert in same table with a autoincrement field in MySQL?

I&#39;m looking at Amazon&#39;s DynamoDB as it looks like it takes away all of the hassle of maintaining and scaling your database server. I&#39;m currently using MySQL, and maintaining and scaling the database is a complete headache.

I&#39;ve gone through the documentation and I&#39;m having a hard time trying to wrap my head around how you would structure your data so it could be easily retrieved.

I&#39;m totally new to NoSQL and non-relational databases.

From the Dynamo documentation it sounds like you can only query a table on the primary hash key, and the primary range key with a limited number of comparison operators. 

Or you can run a full table scan and apply a filter to it. The catch is that it will only scan 1Mb at a time, so you&#39;d likely have to repeat your scan to find X number of results.

I realize these limitations allow them to provide predictable performance, but it seems like it makes it really difficult to get your data out. And performing full table scans *seems* like it would be really inefficient, and would only become less efficient over time as your table grows.

For Instance, say I have a Flickr clone. My Images table might look something like:

 - Image ID (Number, Primary Hash Key)
 - Date Added (Number, Primary Range Key)
 - User ID (String)
 - Tags (String Set)
 - etc

So using query I would be able to list all images from the last 7 days and limit it to X number of results pretty easily.

But if I wanted to list all images from a particular user I would need to do a full table scan and filter by username. Same would go for tags.

And because you can only scan 1Mb at a time you may need to do multiple scans to find X number of images. I also don&#39;t see a way to easily stop at X number of images. If you&#39;re trying to grab 30 images, your first scan might find 5, and your second may find 40. 

Do I have this right? Is it basically a trade-off? You get really fast predictable database performance that is virtually maintenance free. But the trade-off is that you need to build way more logic to deal with the results?

Or am I totally off base here?

How do you query DynamoDB?

I&#39;m writing a simple logging service in DynamoDB.

I have a logs table that is keyed by a user_id hash and a timestamp (Unix epoch int) range.

When a user of the service terminates their account, I need to delete all items in the table, regardless of the range value.

What is the recommended way of doing this sort of operation (Keeping in mind there could be millions of items to delete)?

My options, as far as I can see are:

A: Perform a Scan operation, calling delete on each returned item, until no items are left

B: Perform a BatchGet operation, again calling delete on each item until none are left

Both of these look terrible to me as they will take a long time.

What I ideally want to do is call LogTable.DeleteItem(user_id) - Without supplying the range, and have it delete everything for me.


What is the recommended way to delete a large number of items from DynamoDB?

There&#39;s a typo in my MongoDB database name and I&#39;m looking to rename the database.

I can [copy][1] and delete like so...

    db.copyDatabase(&#39;old_name&#39;, &#39;new_name&#39;);
    use old_name
    db.dropDatabase();

Is there a command to rename a database?

  [1]: http://www.mongodb.org/display/DOCS/Copy+Database+Commands

How do you rename a MongoDB database?

How can I test an UPDATE statement for example to see if it would work, for example if it would actually update rows etc?

Is there a way to simulate it easily?

How to test run an UPDATE statement in PostgreSQL?

In my Rails (3.2) app, I have a bunch of tables in my database but I forgot to add a few not null constraints. How can I write a migration which adds not null to an existing column?

Ruby on Rails: How do I add a not null constraint to an existing column using a migration?

&gt; **Possible Duplicate:**  
&gt; [R: Multiline Comment Workarounds?](https://stackoverflow.com/questions/1231195/r-multiline-comment-workarounds)  

&lt;!-- End of automatically inserted text --&gt;

I want to comment out several lines of code in R. Is there any way of doing it without having to put a # before each line - sort of like `/* blocked out code */` in SAS?

R: Comment out block of code

I&#39;d like to add comments for a few packages in a pip requirements file. (Just to explain why that package is on the list.) Can I do this?

I&#39;m imagining something like

&lt;pre&gt;&lt;code&gt;Babel==0.9.5 # translation
CherryPy==3.2.0 # web server
Creoleparser==0.7.1 # wiki formatting
Genshi==0.5.1 # templating
&lt;/code&gt;&lt;/pre&gt;

Can I add comments to a pip requirements file?

I know how to write a multi-line command in a Bash script, but how can I add a comment for each line in a multiline command?

    CommandName InputFiles      \ # This is the comment for the 1st line
                --option1 arg1  \ # This is the comment for the 2nd line
                --option2 arg2    # This is the comment for the 3nd line

But unfortunately, the comment after continuation character `\` will break the command.



How to put a line comment for a multi-line command

So I only recently discovered the TODO comment. For those of you that don&#39;t know, most modern IDE&#39;s will recognize this word in a comment and flag the comment line a different colour so It stands out.

EG.
    
    //Need to talk to Bill about refactoring this code

    //TODO:Need to talk to Bill about refactoring this code

You may notice in IDE&#39;s like [Eclipse][1] or [Rubymine][2] highlight the TODO comment and some nice other features to do with it.


My question is: What other keywords are there like the TODO? It seems like a much better way of communicating to developers through comments and a feature that should be a bit more widely known in IDE&#39;s. Their purpose is to help with development after all..


  [1]: http://eclipse.org/
  [2]: http://www.jetbrains.com/ruby/

IDE comment keywords

    &lt;!-- here is some comment --
                                ^
                                |
                        what can be here apart from &#39;&gt;&#39;?

XML seems not to like &#39;--&#39; inside comments. I read somewhere that &#39;--&#39; switchs some modes inside `&lt;! ... &gt;` thing, but `&lt;!-- -- -- --&gt;` (even number of `--`s) seem to be invalid too. If it is some historic feature, what is &quot;pro&quot; part of it? (&quot;contra&quot; part is inability to have `--` in comments).

What is the reason of complicating comment processing by not making just &#39;--&gt;&#39; end of comment and allowing &#39;--&#39; inside?

Content Type	Original Author	Original Content on Stackoverflow
Question	amir amir	View Question on Stackoverflow
Solution 1 - Mysql	Martti Laine	View Answer on Stackoverflow
Solution 2 - Mysql	user1178831	View Answer on Stackoverflow
Solution 3 - Mysql	fivedigit	View Answer on Stackoverflow
Solution 4 - Mysql	Bort	View Answer on Stackoverflow
Solution 5 - Mysql	rivethead_	View Answer on Stackoverflow
Solution 6 - Mysql	Mr Coder	View Answer on Stackoverflow

How can I add comments in MySQL?

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

Solution 4 - Mysql

Solution 5 - Mysql

Solution 6 - Mysql

How to check if mod_rewrite is enabled in php?

Why doesn't ruby support method overloading?

Attributions