Surround that select with parentheses.

    SET @v1 := (SELECT COUNT(*) FROM user_rating);
    SELECT @v1;

Additionally, if you want to set multiple variables at once by one query, you can use the other syntax for setting variables which goes like this: `SELECT @varname:=value`.

A practical example:

    SELECT @total_count:=COUNT(*), @total_price:=SUM(quantity*price) FROM items ...


use this 

     SELECT weight INTO @x FROM p_status where tcount=&#39;value&#39; LIMIT 1;

tested and workes fine...

    Select count(*) from table_name into @var1; 
    Select @var1;

    map&lt;string, string&gt; dada;
    dada[&quot;dummy&quot;] = &quot;papy&quot;;
    cout &lt;&lt; dada[&quot;pootoo&quot;];

I&#39;m puzzled because I don&#39;t know if it&#39;s considered undefined behaviour or not, how to know when I request a key which does not exist, do I just use find instead ?

What happens if I read a map&#39;s value where the key does not exist?

Say I have a list `x` with unkown length from which I want to randomly pop one element so that the list does not contain the element afterwards. What is the most pythonic way to do this?

I can do it using a rather unhandy combincation of `pop`, `random.randint`, and `len`, and would like to see shorter or nicer solutions:

    import random
    x = [1,2,3,4,5,6]
    x.pop(random.randint(0,len(x)-1))

 What I am trying to achieve is consecutively pop random elements from a list. (i.e., randomly pop one element and move it to a dictionary, randomly pop another element and move it to another dictionary, ...)


Note that I am using Python 2.6 and did not find any solutions via the search function.

What is the most pythonic way to pop a random element from a list?

    SET @v1 := SELECT COUNT(*) FROM user_rating;
    SELECT @v1

When I execute this query with `set` variable this error is shown.

    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 &#39;SELECT count(*) FROM user_rating&#39; at line 1

    Execution Time : 00:00:00:000
    Transfer Time  : 00:00:00:000
    Total Time     : 00:00:00:000

    (1 row(s) returned)
    Execution Time : 00:00:00:343
    Transfer Time  : 00:00:00:000
    Total Time     : 00:00:00:343

How to store Query Result in variable using mysql

<pre><code class="hljs language-sql">SET @v1 := SELECT COUNT(*) FROM user_rating;
SELECT @v1
</code></pre>
When I execute this query with <code>set</code> variable this error is shown.
<pre><code class="hljs language-sql">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 'SELECT count(*) FROM user_rating' at line 1

Execution Time : 00:00:00:000
Transfer Time : 00:00:00:000
Total Time : 00:00:00:000

(1 row(s) returned)
Execution Time : 00:00:00:343
Transfer Time : 00:00:00:000
Total Time : 00:00:00:343
</code></pre>

This is what I&#39;ve read so far about [`PDO::ATTR_EMULATE_PREPARES`](http://www.php.net/manual/en/pdo.setattribute.php):

1. [PDO&#39;s prepare emulation is better for performance since MySQL&#39;s native prepare bypasses the query cache][1].
2. [MySQL&#39;s native prepare is better for security (preventing SQL Injection)][2].
3. [MySQL&#39;s native prepare is better for error reporting][3].

I don&#39;t know how true any of these statements are anymore. My greatest concern in choosing a MySQL interface is preventing SQL Injection. The second concern is performance.

My application currently uses procedural MySQLi (without prepared statements), and utilizes the query cache quite a bit. It will rarely re-use prepared statements in a single request. I started the move to PDO for the named parameters and security of prepared statements.

I&#39;m using `MySQL 5.1.61` and `PHP 5.3.2`

Should I leave `PDO::ATTR_EMULATE_PREPARES` enabled or not? Is there a way to have both the performance of the query cache and the security of prepared statements?

  [1]: https://stackoverflow.com/a/5751895
  [2]: https://stackoverflow.com/a/1314549
  [3]: https://stackoverflow.com/questions/3727186/the-way-pdo-parametrized-query-works

PDO MySQL: Use PDO::ATTR_EMULATE_PREPARES or not?

In the query below:

    SELECT column 
    FROM table
    LIMIT 18 OFFSET 8

how many results will we get as output and from where to where?







Which rows are returned when using LIMIT with OFFSET in MySQL?

I have to get last 5 numbers using mysql.

My values are like `YOT-A78514`,`LOP-C4521` ...

I have to get only last five char . How can I do this in query?

Getting last 5 char of string with mysql query

I want to create a new table with properties of an old table and without duplicates. I want to do something like this:

    CREATE TABLE New_Users  LIKE Old_Users, 
    AS
    (SELECT * FROM Old_Users GROUP BY ID) ;

But the above is not working.  Can anybody modify it to work?

CREATE TABLE LIKE A1 as A2

I am using Hotaru CMS with the Image Upload plugin, I get this error if I try to attach an image to a post, otherwise there is no error:

&gt; unserialize() [function.unserialize]: Error at offset

The offending code (error points to line with **):

    /**
         * Retrieve submission step data
         *
         * @param $key - empty when setting
         * @return bool
         */
        public function loadSubmitData($h, $key = &#39;&#39;)
        {
            // delete everything in this table older than 30 minutes:
            $this-&gt;deleteTempData($h-&gt;db);
            
            if (!$key) { return false; }
            
            $cleanKey = preg_replace(&#39;/[^a-z0-9]+/&#39;,&#39;&#39;,$key);
            if (strcmp($key,$cleanKey) != 0) {
                return false;
            } else {
                $sql = &quot;SELECT tempdata_value FROM &quot; . TABLE_TEMPDATA . &quot; WHERE tempdata_key = %s ORDER BY tempdata_updatedts DESC LIMIT 1&quot;;
                $submitted_data = $h-&gt;db-&gt;get_var($h-&gt;db-&gt;prepare($sql, $key));
                **if ($submitted_data) { return unserialize($submitted_data); } else { return false; }** 
            }
        }

Data from the table, notice the end bit has the image info, I am not an expert in PHP so I was wondering what you guys/gals might think?

tempdata_value:

    a:10:{s:16:&quot;submit_editorial&quot;;b:0;s:15:&quot;submit_orig_url&quot;;s:13:&quot;www.bbc.co.uk&quot;;s:12:&quot;submit_title&quot;;s:14:&quot;No title found&quot;;s:14:&quot;submit_content&quot;;s:12:&quot;dnfsdkfjdfdf&quot;;s:15:&quot;submit_category&quot;;i:2;s:11:&quot;submit_tags&quot;;s:3:&quot;bbc&quot;;s:9:&quot;submit_id&quot;;b:0;s:16:&quot;submit_subscribe&quot;;i:0;s:15:&quot;submit_comments&quot;;s:4:&quot;open&quot;;s:5:&quot;image&quot;;s:19:&quot;C:fakepath100.jpg&quot;;}

Edit: I think I&#39;ve found the serialize bit...

    /**
         * Save submission step data
         *
         * @return bool
         */
        public function saveSubmitData($h)
        {
            // delete everything in this table older than 30 minutes:
            $this-&gt;deleteTempData($h-&gt;db);
    
            $sid = preg_replace(&#39;/[^a-z0-9]+/i&#39;, &#39;&#39;, session_id());
            $key = md5(microtime() . $sid . rand());
            $sql = &quot;INSERT INTO &quot; . TABLE_TEMPDATA . &quot; (tempdata_key, tempdata_value, tempdata_updateby) VALUES (%s,%s, %d)&quot;;
            $h-&gt;db-&gt;query($h-&gt;db-&gt;prepare($sql, $key, serialize($h-&gt;vars[&#39;submitted_data&#39;]), $h-&gt;currentUser-&gt;id));
            return $key;
        }

How to repair a serialized string which has been corrupted by an incorrect byte count length?

How to change the column size of the `salary` column in the `employee` table from `numeric(18,0)` to `numeric(22,5)`



Altering column size in SQL Server

I have 2 commands and need both of them executed correctly or none of them executed. So I think I need a transaction, but I don&#39;t know how to use it correctly.

What&#39;s the problem with the following script?
    
    BEGIN TRANSACTION [Tran1]

    INSERT INTO [Test].[dbo].[T1]
        ([Title], [AVG])
    VALUES (&#39;Tidd130&#39;, 130), (&#39;Tidd230&#39;, 230)

    UPDATE [Test].[dbo].[T1]
      SET [Title] = N&#39;az2&#39; ,[AVG] = 1
      WHERE [dbo].[T1].[Title] = N&#39;az&#39;

    COMMIT TRANSACTION [Tran1]
    GO

The `INSERT` command is executed, but the `UPDATE` command has a problem.

How can I implement this to rollback both commands if any of them have an error in execution?

Correct use of transactions in SQL Server

I am having a hard time understanding the difference between &#39;row-level triggers&#39; and &#39;statement-level triggers&#39;. 

From my understanding, in the scenario a statement level trigger is created, the whole table can be modified. A row level trigger would only allow me to modify the tuple being affect by the trigger&#39;s specified event. 

Is this correct? 
Does anyone have an example of the two?


row-level trigger vs statement-level trigger

Which of the following options, if any, is considered best practice when designing a table used to store user settings? 

(OPTION 1)

    USER_SETTINGS
    -Id
    -Code (example &quot;Email_LimitMax&quot;)
    -Value (example &quot;5&quot;)
    -UserId

(OPTION 2) 

create a new table for each setting where, for example, notification settings would require you to create:

    &quot;USER_ALERT_SETTINGS&quot;
    -Id
    -UserId
    -EmailAdded (i.e true)
    -EmailRemoved 
    -PasswordChanged
    ...
    ...

    &quot;USER_EMAIL_SETTINGS&quot;
    -Id
    -UserId
    -EmailLimitMax
    ....

(OPTION 3)

    &quot;USER&quot;
    -Name
    ...
    -ConfigXML


Database design for user settings

I am trying to create a new database from an old backup of database on the same server.
When using *SQL server management studio* and trying to restore to the new DB from the backup I get this error


    System.Data.SqlClient.SqlError: The backup set holds a backup of a database 
    other than the existing &#39;test&#39; database. (Microsoft.SqlServer.Smo)

after googling around I found this piece of code

        RESTORE DATABASE myDB

     FROM DISK = &#39;C:\myDB.bak&#39;

     WITH MOVE &#39;myDB_Data&#39; TO &#39;C:\DATA\myDB.mdf&#39;,

    MOVE &#39;myDB_Log&#39; TO &#39;C:\DATA\myDB_log.mdf&#39;
    GO


I was wondering will the move statements mess with the database that the backup came from on that server?

Thanks, all help appreciated.


Creating new database from a backup of another Database on the same server?

I am looking for a clean way to use variables within a multiline Python string. Say I wanted to do the following:

    string1 = go
    string2 = now
    string3 = great

    &quot;&quot;&quot;
    I will $string1 there
    I will go $string2
    $string3
    &quot;&quot;&quot;

I&#39;m looking to see if there is something similar to `$` in Perl to indicate a variable in the Python syntax.

If not - what is the cleanest way to create a multiline string with variables?

How do I create a multiline Python string with inline variables?

I would like to get the SRC attribute into a variable in this example:

    &lt;img border=&quot;0&quot; src=&quot;/images/image.jpg&quot; alt=&quot;Image&quot; width=&quot;100&quot; height=&quot;100&quot; /&gt;

So for example - I would like to get a variable `$foo = &quot;/images/image.jpg&quot;`.
Important! The src attribute will be **dynamic**, so it mustn&#39;t be hardcoded.
Is there any quick and easy way to do this?

Thanks!

EDIT: The image will be a part of a huge string that is basically the content of a news story. So the image is just a part of that.

EDIT2: There will be more images in this string, and I would only want to get the src of the first one. Is this possible?

Get img src with PHP

      
How can I use a variable to remove all instances of a substring from a string?
(to remove, I&#39;m thinking the best way is to replace, with nothing, globally... right?)

if I have these 2 strings,  

    myString = &quot;This sentence is an example sentence.&quot;
    oldWord = &quot; sentence&quot;

then something like this

    myString.replace(oldWord, &quot;&quot;);
only replaces the first instance of the variable in the string.

but if I add the global g like this `myString.replace(/oldWord/g, &quot;&quot;);` it doesn&#39;t work, because it thinks oldWord, in this case, is the substring, not a variable. How can I do this with the variable?

myString.replace( VARIABLE, &quot;&quot;) ...... but globally

I am a beginner to assembly and I don&#39;t know what all the db, dw, dd, things mean.
I have tried to write this little script that does 1+1, stores it in a variable and then displays the result. Here is my code so far:

    .386
    .model flat, stdcall 
    option casemap :none
    include \masm32\include\windows.inc
    include \masm32\include\kernel32.inc
    include \masm32\include\masm32.inc
    includelib \masm32\lib\kernel32.lib
    includelib \masm32\lib\masm32.lib
    .data
    num db ? ; set variable . Here is where I don&#39;t know what data type to use.
    .code
    start:
    mov eax, 1               ; add 1 to eax register
    mov ebx, 1               ; add 1 to ebx register
    add eax, ebx             ; add registers eax and ebx
    push eax                 ; push eax into the stack
    pop num                  ; pop eax into the variable num (when I tried it, it gave me an error, i think  thats because of the data type)
    invoke StdOut, addr num  ; display num on the console.
    invoke ExitProcess       ; exit
    end start

I need to understand what the db, dw, dd things mean and how they affect variable setting and combining and that sort of thing.

Thanks in advance,
Progrmr 

Which variable size to use (db, dw, dd) with x86 assembly?

I&#39;m trying to do something very simple and yet, after an hour of so of searching a I can&#39;t find a suitable answer so I must be missing something fairly obvious.

I&#39;m trying to dynamically create filenames for use with ifstream. Whilst I understand various methods are available of doing this, I have settled on creating a std::string, and the using stringname.c_str to convert to const.

The problem is however that I need to create the string with a mix of variables and predefined text values. I&#39;m getting compiler errors, so this must be a syntax issue.

Pseudo 

    std::string var = &quot;sometext&quot; + somevar + &quot;sometext&quot; + somevar;

Thanks!

C++ create string of text and variables

Does a Java Set retain order?  A method is returning a Set to me and supposedly the data is ordered but iterating over the Set, the data is unordered.  Is there a better way to manage this? Does the method need to be changed to return something other than a Set?

Java Set retain order?

I want to know the comparison between List and Set in terms of performance,memory allocation and usability.

If i don&#39;t have any requirement of keeping the uniqueness in the list of objects, neither required the insertion order to be maintained, Can I use ArrayList and SortedSet/HashSet interchangeably?
Will it be good to directly use Collections class instead of even list/set?

P.S. I also don&#39;t have any need for list or set specific functions provided by java.
I am using List/Set instead of Array only because they can dynamically grow without extra programming efforts.



Performance and Memory allocation comparison between List and Set

    Iterator ite = Set.iterator();
    Iterator ite = List.iterator();
    
    ListIterator listite = List.listIterator();

We can use `Iterator` to traverse a `Set` or a `List` or a `Map`. But `ListIterator` can only be used to traverse a `List`, it can&#39;t traverse a `Set`. Why?

I know that the main difference is that with iterator we can travel in only one direction but with `ListIterator` we can travel both directions. Are there any other differences? And any advantages of `ListIterator` over `Iterator`?


Difference between Iterator and Listiterator?

After creating a struct like this:

    type Foo struct {
    	name string
    }
    
    func (f Foo) SetName(name string) {
    	f.name = name
    }
    
    func (f Foo) GetName() string {
    	return f.name
    }

How do I create a new instance of Foo and set and get the name?
I tried the following:


	p := new(Foo)
	p.SetName(&quot;Abc&quot;)
	name := p.GetName()

	fmt.Println(name)


Nothing gets printed, because name is empty. So how do I set and get a field inside a struct?
    
[Working playground](https://play.golang.org/p/_xkIc-n6Wbk)

How to set and get fields in struct&#39;s method

It [appears](https://stackoverflow.com/q/1433978/1593077) that MySQL doesn&#39;t have array variables. What should I use instead? 

------
There seem to be two alternatives suggested: A **set-type scalar** and **temporary tables**. The question I linked to suggests the former. But is it good practice to use these instead of array variables? Alternatively, if I go with sets, what would be the set-based idiom equivalent to `foreach`? 

Content Type	Original Author	Original Content on Stackoverflow
Question	Query Master	View Question on Stackoverflow
Solution 1 - Mysql	Sergio Tulentsev	View Answer on Stackoverflow
Solution 2 - Mysql	Yirkha	View Answer on Stackoverflow
Solution 3 - Mysql	Aman Maurya	View Answer on Stackoverflow
Solution 4 - Mysql	Kesha Viveki	View Answer on Stackoverflow

How to store Query Result in variable using mysql

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

Solution 4 - Mysql

What is the most pythonic way to pop a random element from a list?

What happens if I read a map's value where the key does not exist?

Attributions