`||` represents string concatenation. Unfortunately, string concatenation is not completely portable across all sql dialects:

  - ansi sql: `||` (infix operator)
  - mysql: `concat` ( vararg function ). **caution**: `||` means &#39;logical or&#39; ([It&#39;s configurable](http://dev.mysql.com/doc/refman/5.7/en/sql-mode.html#sqlmode_pipes_as_concat), however; thanks to [@hvd](https://stackoverflow.com/users/743382/hvd) for pointing that out)
  - oracle: `||` (infix operator), `concat` ( **caution**: function of arity 2 only ! )
  - postgres:  `||` (infix operator)
  - sql server: `+` (infix operator), `concat` ( vararg function )
  - sqlite: `||` (infix operator)

hopefully the confusion is complete ...


It is a concat statement.  It will concatenate the two strings.

Here is a helpful post!

https://stackoverflow.com/questions/11403931/what-is-the-difference-between-operator-and-concat-function-in-oracle

SELECT &#39;a&#39; || &#39;,&#39; || &#39;b&#39; AS letter 
will combine a letter. 
The result become &#39;a,b&#39;

It&#39;s a concatenation operator.  So you would get &#39;a,b&#39; from that.
I think `||` will work on *most* RDBMS&#39;s.  SQL Server requires the `+` operator (thanks to HVD for setting me straight!).


In Oracle, SQLite3, and MySQL, it concatenates strings. Please see the [Oracle documentation][1].  The [MySQL documentation][2].

Also, it&#39;s part of ANSI SQL, but [read this for more information][3]. 


  [1]: http://docs.oracle.com/cd/B19306_01/server.102/b14200/operators003.htm
  [2]: http://dev.mysql.com/doc/refman/5.1/en/sql-mode.html#sqlmode_pipes_as_concat
  [3]: https://drupal.org/node/809698

in oracle its a shortcut for concatenate

http://docs.oracle.com/cd/B19306_01/server.102/b14200/operators003.htm

I&#39;m working on a service in WebAPI 2, and the endpoint currently returns an `IHttpActionResult`.  I&#39;d like to return a status code `422`, but since it&#39;s not in the `HttpStatusCode` enumeration, I&#39;m at a loss as to how it would be sent, since all of the constructors require a parameter of `HttpStatusCode`

As it stands now, I&#39;m returning `BadResult(message)`, but returning a `422` + message would be more descriptive and useful for my clients.  Any ideas?

Return Custom HTTP Status Code from WebAPI 2 endpoint

in Intel 64 architecture there is the rax..rdx registers which are simply A..D general purpose registers.

But there are also registers called rsi and rdi which are the &quot;source index&quot; and &quot;destination index&quot; registers. why do these registers have actual names (compared to just A, etc)?  
What does &quot;source index&quot; and &quot;destination index&quot; actually mean? And is there some convention that says these registers should be used in specific circumstances?

Intel 64, rsi and rdi registers

What does `||` do in SQL?

    SELECT &#39;a&#39; || &#39;,&#39; || &#39;b&#39; AS letter

What does SQL Select symbol || mean?

What does <code>||</code> do in SQL?
<pre><code class="hljs language-sql">SELECT 'a' || ',' || 'b' AS letter
</code></pre>

I have installed **Python version** **3.4.0** and I would like to do a project with MySQL database. I downloaded and tried installing **MySQLdb**, but it wasn&#39;t successful for this version of Python.

Any suggestions how could I fix this problem and install it properly?

Python 3.4.0 with MySQL database

I know this question has been asked a lot of times 

I followed Most of the answers in the internet But I still get the same Message

&gt; 403 Forbidden
&gt; 
&gt; You don&#39;t have permission to access / on this server.


It is weird that when I access using the same PC to **`localhost:1234`** it runs normally but if I access using my IP address **`192.168.0.188:1234`** 

Also which is really weird is that I tried to install WAMP on other PC and without any configuration I could access to that PC.

So I thought it&#39;s because McAfee and Firewall so I open port on Widows and McAfee and nothing changed also I turned off Firewall and still nothing change.

Then for no reason I opened  port through the Router “port forwarding” and still nothing changed.

I don&#39;t think that it&#39;s because my configuration in WAMP since I am still able to get this `403 Forbidden` Message and also by using other PC without any configuration I could access it.

***Both PCs are setup like this:***

**Windows 8 Pro**

 - **WAMP Wampserver:** 2.4 
 - **Apache Version:** 2.4.4  
 - **PHP Version:** 5.4.12  
 - **MySQL Version:** 5.6.12  

The accessible PC uses *Microsoft Security Essentials*.

The inaccessible PC uses *McAfee Internet Security*.

I tried to turn **off WAMP** and **start IIS** For Microsoft Server (I works perfectly From any PC) but WAMP is still not not working

I followed these tutorial: 

 - [How to Access WAMP Server in LAN or WAN][1]
 - [Install &amp; Setup Virtual Host Guide for WAMP][2]
 - [Install &amp; Setup LAN &amp; Worldwide Access Guide for WAMP][3]

And the Stack Overflow answers here: 

 - [Cannot access wamp server on local network][4]
 - [WAMP 403 Forbidden message on Windows 7][5]


  [1]: http://www.codeproject.com/Tips/395286/How-to-Access-WAMP-Server-in-LAN-or-WAN
  [2]: http://guides.jlbn.net/setvh/setvh1.html
  [3]: http://guides.jlbn.net/setaccess/setaccess1.html
  [4]: https://stackoverflow.com/questions/8219062/cannot-access-wamp-server-on-local-network
  [5]: https://stackoverflow.com/questions/8204902/wamp-403-forbidden-message-on-windows-7

WAMP Cannot access on local network 403 Forbidden

When issuing a command to MySQL, I&#39;m getting error #1064 &quot;syntax error&quot;.

1. What does it mean?

2. How can I fix it?

How can I fix MySQL error #1064?

I have an existing MySQL instance (test), containing 2 databases and a few users each having different access privileges to each database.

I now need to duplicate one of the databases (into production) **and the users** associated with it.

Duplicating the database was [easy][1]:

Export:

    mysqldump --no-data --tables -u root -p secondb &gt;&gt; secondb_schema.sql

Import:

    mysql -u root -p -h localhost secondb &lt; secondb_schema.sql


I didn&#39;t find, however, a straightforward way to export and import **users**, from the **command line** (either inside or outside mysql).

How do I export and import a [user][2], from the command line?

---------

**Update**: So far, I have found manual (and thus error prone) steps for accomplishing this:

    -- lists all users
    select user,host from mysql.user;

Then find its grants:

    -- find privilege granted to a particular user
    show grants for &#39;root&#39;@&#39;localhost&#39;; 


Then **manually** create user with the grants listed in the result of the &#39;show grants&#39; command above. 

I prefer a safer, more automated way. Is there one?

  [1]: https://stackoverflow.com/a/21091197/1864054
  [2]: https://stackoverflow.com/a/1135251/1864054




How to Export &amp; Import Existing User (with its Privileges!)

I have table with `player`-s in many-to-many relation with `skill`-s

The goal is to list the players and their &quot;top 3 skills&quot; with a single query.

[fiddle][1]

    create table player(
      id int primary key
    );
    
    create table skill(
      id int primary key,
      title varchar(100)
    );
    
    create table player_skills (
      id int primary key,
      player_id int,
      skill_id int,
      value int
    );

Query:

    SELECT 
    p.id,  
    group_concat(s.title  SEPARATOR &#39;, &#39;) as skills
    
    FROM player p
    LEFT JOIN player_skills ps ON ps.player_id = p.id
    LEFT JOIN skill s ON s.id = ps.skill_id
    
    WHERE ps.value &gt; 2
    -- skills limit 3 some how ...
    group by p.id 
    order by s.id
    
    
    -- expected result
    -- player_ID, skills
    -- 1 , &#39;one&#39;
    -- 2 , &#39;one&#39;
    -- 3 , &#39;two, three, four&#39;

As you can see in the fiddle the result of the query is missing only the limit of 3 skills.  
I tried several variation of sub queries.. joins and so but with no effect.



  [1]: http://sqlfiddle.com/#!2/f3f41/6


GROUP_CONCAT with limit

I have a postgresql function

    CREATE OR REPLACE FUNCTION fixMissingFiles() RETURNS VOID AS $$
	DECLARE
		deletedContactId integer;
        BEGIN
		        SELECT INTO deletedContactId contact_id FROM myContacts WHERE id=206351;
		
                -- print the value of deletedContactId variable to the console

        END;
    $$ LANGUAGE plpgsql;

How can I print the value of the deletedContactId to the console?

printing a value of a variable in postgresql

I need to remove some attributes from a json type column.

The Table:

    CREATE TABLE my_table( id VARCHAR(80), data json);
    INSERT INTO my_table (id, data) VALUES (
      &#39;A&#39;, 
      &#39;{&quot;attrA&quot;:1,&quot;attrB&quot;:true,&quot;attrC&quot;:[&quot;a&quot;, &quot;b&quot;, &quot;c&quot;]}&#39;
    );

Now, I need to remove `attrB` from column `data`.

Something like `alter table my_table drop column data-&gt;&#39;attrB&#39;;` would be nice. But a way with a temporary table would be enough, too.

PostgreSQL: Remove attribute from JSON column

As I can understand [documentation][1] the following definitions are equivalent:

    create table foo (
        id serial primary key,
        code integer,
        label text,
        constraint foo_uq unique (code, label));

    create table foo (
        id serial primary key,
        code integer,
        label text);
    create unique index foo_idx on foo using btree (code, label);    

However, a note in [the manual for Postgres 9.4][2] says:

&gt; The preferred way to add a unique constraint to a table is `ALTER TABLE ... ADD CONSTRAINT`. The use of indexes to enforce unique constraints
&gt; could be considered an implementation detail that should not be
&gt; accessed directly.

(Edit: this note was removed from the manual with Postgres 9.5.)

Is it only a matter of good style? What are practical consequences of choice one of these variants (e.g. in performance)?


  [1]: https://www.postgresql.org/docs/current/indexes-unique.html
  [2]: https://www.postgresql.org/docs/9.4/indexes-unique.html

Postgres unique constraint vs index

I&#39;m installing SQL Server 2012 at the moment and when I was about to run the installation, this error pops up: 

![The errors can be seen clearly in this picture][1]


On clicking the first failed test, which is &quot;Reporting Services Catalog Database File Existence&quot;, this is what i get:

![enter image description here][2]


On clicking the second failed test, which is &quot;Reporting Services Catalog Temporary Database File Existence&quot;, this is what i get:

![enter image description here][3]


  [1]: http://i.stack.imgur.com/rgr1C.png
  [2]: http://i.stack.imgur.com/Ipmqu.png
  [3]: http://i.stack.imgur.com/MV3XS.png

So basically, both of the message box says me that &quot;Catalog Database File&quot; &amp; &quot;Catalog Temporary database files exists&quot;. Because of this, i need to select Reporting Services file-only mode installation. 

My questions are:

 1. How do i select file-only mode installation?
 2. Do i&#39;ve to close the setup and do something and afterwards run the setup again?
 
Btw, I had SQL Server 2012 installed before. I uninstalled it completely due to some strange errors and decided to reinstall a fresh copy of SQL Server 2012 and now I&#39;m stuck with these errors. Any help will be sincerely appreciated. :)

SQL Server 2012 installation Reporting Services Catalog error

I am trying to use an `inner join` a view and a table using the following query

    SELECT 
       AcId, AcName, PldepPer, RepId, CustCatg, HardCode, BlockCust, CrPeriod, CrLimit, 
       BillLimit, Mode, PNotes, gtab82.memno 
    FROM
       VCustomer 
    INNER JOIN   
       vcustomer AS v1 ON gtab82.memacid = v1.acid 
    WHERE (AcGrCode = &#39;204&#39; OR CreDebt = &#39;True&#39;) 
    AND Masked = &#39;false&#39;
    ORDER BY AcName

and the error is

    missing FROM-clause entry for table &quot;gtab82&quot;

missing FROM-clause entry for table

I am trying to connect my grails project to Oracle databse(**Oracle 12c**) in windows(8) system. However, whenever I run my application I get following exception :

    Caused by: org.apache.commons.dbcp.SQLNestedException: 
    Cannot create PoolableConnectionFactory (ORA-28040: 
    No matching authentication protocol)

    Caused by: 
    java.sql.SQLException: ORA-28040: 
    No matching authentication protocol


According to internet suggestion I also tried editing my  **`*.ora`** file but it is not working.

I added following snippet in **`sqlnet.ora`** file :

    SQLNET.ALLOWED_LOGON_VERSION=10
    SQLNET.ALLOWED_LOGON_VERSION_CLIENT=10
    SQLNET.ALLOWED_LOGON_VERSION_SERVER=10

Here i tried assigning (10,11,12) but neither of them is working.

Can anyone please help me with this ?

ORA-28040: No matching authentication protocol exception

can anybody explain what is the main difference between functions and procedures in Oracle? Why must I use procedures if I can do everything with functions? 

 
 1. If I cannot call procedure in sql statement, ok, I&#39;ll write a function to do the same work.
 2. Procedures don&#39;t return values, ok, I&#39;ll return only sql%rowcount or 1(success), 0(exception) after any dml operation
 3. Both procedures and functions can pass variables to calling environment via OUT/IN OUT parameters

I heard that the main difference is in performance, &#39;procedures are faster than functions&#39;. But without any detail. 

Thanks in advance.

Functions vs procedures in Oracle

I am getting the error :

     ORA-28000: the account is locked 

**Is this a DB Issue?** When I unlock user account using the command `ALTER USER username ACCOUNT UNLOCK` temporarily it will be OK. Then after some time the same account lock happens again.

The database using is oracle `XE`

**Does anybody else have the same issue?** 





ORA-28000: the account is locked error getting frequently

My requirement is to get each client&#39;s latest order, and then get top 100 records.

I wrote one query as below to get latest orders for each client. Internal query works fine. But I don&#39;t know how to get first 100 based on the results.

        SELECT * FROM (
          SELECT id, client_id, ROW_NUMBER() OVER(PARTITION BY client_id ORDER BY create_time DESC) rn 
          FROM order
        ) WHERE rn=1

Any ideas? Thanks.


How to Select Top 100 rows in Oracle?

I tried to generate some test data by running the following sql.

    BEGIN    
      FOR i IN 1..8180 LOOP
        insert into SPEEDTEST
        select &#39;column1&#39;, &#39;column2&#39;, &#39;column3&#39;, &#39;column4&#39;, &#39;column5&#39;, &#39;column6&#39;, &#39;column7&#39;, &#39;column8&#39;, &#39;column9&#39;, &#39;column10&#39;, &#39;column11&#39;, &#39;column12&#39;, &#39;column13&#39;, &#39;column14&#39;, &#39;column15&#39;, &#39;column16&#39;, &#39;column17&#39;, &#39;column18&#39;, &#39;column19&#39;, &#39;column20&#39;, &#39;column21&#39;, &#39;column22&#39;, &#39;column23&#39;, &#39;column24&#39;, &#39;column25&#39;, &#39;column26&#39;, &#39;column27&#39;, &#39;column28&#39;, &#39;column29&#39;, &#39;column30&#39;, &#39;column31&#39;, &#39;column32&#39;, &#39;column33&#39;, &#39;column34&#39;, &#39;column35&#39;, &#39;column36&#39;, &#39;column37&#39;, &#39;column38&#39;, &#39;column39&#39;, &#39;column40&#39;, &#39;column41&#39;, &#39;column42&#39;, &#39;column43&#39;, &#39;column44&#39;, &#39;column45&#39;, &#39;column46&#39;, &#39;column47&#39;, &#39;column48&#39;, &#39;column49&#39;, &#39;column50&#39;, &#39;column51&#39;, &#39;column52&#39;, &#39;column53&#39;, &#39;column54&#39;, &#39;column55&#39;, &#39;column56&#39;, &#39;column57&#39;, &#39;column58&#39;, &#39;column59&#39;, &#39;column60&#39;, &#39;column61&#39;, &#39;column62&#39;, &#39;column63&#39;, &#39;column64&#39;, &#39;column65&#39;, &#39;column66&#39;, &#39;column67&#39;, &#39;column68&#39;, &#39;column69&#39;, &#39;column70&#39;, &#39;column71&#39;, &#39;column72&#39;, &#39;column73&#39;, &#39;column74&#39;, &#39;column75&#39;, &#39;column76&#39;, &#39;column77&#39;, &#39;column78&#39;, &#39;column79&#39;, &#39;column80&#39;, &#39;column81&#39;, &#39;column82&#39;, &#39;column83&#39;, &#39;column84&#39;, &#39;column85&#39;, &#39;column86&#39;, &#39;column87&#39;, &#39;column88&#39;, &#39;column89&#39;, &#39;column90&#39;, &#39;column91&#39;, &#39;column92&#39;, &#39;column93&#39;, &#39;column94&#39;, &#39;column95&#39;, &#39;column96&#39;, &#39;column97&#39;, &#39;column98&#39;, &#39;column99&#39;, &#39;column100&#39;, i from dual;
      END LOOP;
    END;
    /
    commit;

and it gave me following error:

    ORA-01653: unable to extend table LEGAL.SPEEDTEST by 128 in tablespace LEGAL_DATA
    ORA-06512: at line 4

Which indicates that I ran out of space, **how do I add more and how to know how much do I need? What 128 stands for?**


Content Type	Original Author	Original Content on Stackoverflow
Question	user3586553	View Question on Stackoverflow
Solution 1 - Mysql	collapsar	View Answer on Stackoverflow
Solution 2 - Mysql	John Hartsock	View Answer on Stackoverflow
Solution 3 - Mysql	ivanprakasa	View Answer on Stackoverflow
Solution 4 - Mysql	Andrew	View Answer on Stackoverflow
Solution 5 - Mysql	SQLMason	View Answer on Stackoverflow
Solution 6 - Mysql	Jonathan	View Answer on Stackoverflow

What does SQL Select symbol || mean?

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

Solution 4 - Mysql

Solution 5 - Mysql

Solution 6 - Mysql

Intel 64, rsi and rdi registers

Return Custom HTTP Status Code from WebAPI 2 endpoint

Attributions