    ALTER IGNORE TABLE mytbl ADD UNIQUE (columnName);


----------

**For MySQL 5.7.4 or later:**

    ALTER TABLE mytbl ADD UNIQUE (columnName);

&gt; As of MySQL 5.7.4, the IGNORE clause for ALTER TABLE is removed and
&gt; its use produces an error.

So, make sure to remove duplicate entries first as IGNORE keyword is no longer supported.

[Reference][1]


  [1]: http://dev.mysql.com/doc/refman/5.7/en/alter-table.html#idm140368130931568

Just write this query in your db phpmyadmin.

    ALTER TABLE TableName ADD UNIQUE (FieldName)

Eg: `ALTER TABLE user ADD UNIQUE (email)`


If you also want to name the constraint, use this:

    ALTER TABLE myTable
      ADD CONSTRAINT constraintName 
        UNIQUE (columnName);

`CREATE UNIQUE INDEX foo ON table_name (field_name)`

You have to remove duplicate values on that column before executes that sql.
Any existing duplicate value on that column will lead you to [mysql error 1062](https://stackoverflow.com/search?q=mysql+1062)

The easiest and fastest way would be with phpmyadmin structure table.

![USE PHPMYADMIN ADMIN PANEL!][1]


  [1]: http://i.stack.imgur.com/EKM8H.png

There it&#39;s in Russian language but in English Version  should be the same. Just click Unique button. Also from there you can make your columns PRIMARY or DELETE.

    ALTER IGNORE TABLE mytbl ADD UNIQUE (columnName);

is the right answer 

the insert part 

    INSERT IGNORE INTO mytable ....

This code is to solve our problem to set unique key for existing table 


    alter ignore table ioni_groups add unique (group_name);

I have All Android SDK versions(from 1.5 to 2.3.3), and I tried many methods for getting root in Android emulator. I don&#39;t use any Android device and test everything on emulator(AVD).

I need to get root access in any one of the Android emulator to use the &#39;iptables&#39; and &#39;busybox&#39; functionality. And to use iptables I must have root access. Atleast &#39;su&#39; command should execute in the terminal emulator. 

I also installed `z4root` application, 

But it takes very long time and doesn&#39;t finish rooting, and gets stuck. some say that if we downgrade the system to below RC30, this way we can get root access. if this is true, then how to do this? I use both Linux and Windows OS.

Please someone tell me any method to root my emulator.

How to get root access on Android emulator? 

What is the best way to enable log rotation on a Ruby on Rails production app?

Is it by using logrotate on the hosting server or is there a set of options to use when initialising logger from the app?

Ruby on Rails production log rotation

I have an already existing table with a field that should be unique but is not. I only know this because an entry was made into the table that had the same value as another, already existing, entry and this caused problems. 

How do I make this field only accept unique values?

MySQL - Make an existing Field Unique

<p>I have an already existing table with a field that should be unique but is not. I only know this because an entry was made into the table that had the same value as another, already existing, entry and this caused problems.</p>
<p>How do I make this field only accept unique values?</p>


I&#39;m using a textarea to enable users to input comments.  However, if the users enters new lines, the new lines don&#39;t appear when they are outputted.  Is there any way to make the line breaks stay.

Any idea how do preserve the line breaks?

Preserve Line Breaks From TextArea

Which way to count a number of rows should be faster in MySQL?

This:

    SELECT COUNT(*) FROM ... WHERE ...

Or, the alternative:

    SELECT 1 FROM ... WHERE ...

    // and then count the results with a built-in function, e.g. in PHP mysql_num_rows()

One would think that the first method should be faster, as this is clearly database territory and the database engine should be faster than anybody else when determining things like this internally.

MySQL: Fastest way to count number of rows

Is there a way to detect if a value is a number in a MySQL query? Such as

    SELECT * 
    FROM myTable 
    WHERE isANumber(col1) = true

Detect if value is number in MySQL

How to create a MySQL database dump (`.sql` file) with all its triggers and procedures?

How to export MySQL database with triggers and procedures?

If I run a query with a `between` clause, it seems to exclude the ending value.  
For example:

    select * from person where dob between &#39;2011-01-01&#39; and &#39;2011-01-31&#39;

This gets all results with `dob` from &#39;2011-01-01&#39; till &#39;2011-01-30&#39;; skipping records where `dob` is &#39;2011-01-31&#39;. Can anyone explain why this query behaves this way, and how I could modify it to include records where `dob` is &#39;2011-01-31&#39;? (without adding 1 to the ending date because its been selected by the users.)

MySQL &quot;between&quot; clause not inclusive?

I have SQL Server 2008 R2 and I want to set a unique column.  

There seems to be two ways to do this: &quot;unique index&quot; and &quot;unique constraint&quot;.  They are not much different from what I understand, although unique constraint is recommended by most, because you also get an index automatically.

How do I create a unique constraint?  

    ALTER TABLE Customer ADD CONSTRAINT U_Name UNIQUE(Name)


Is there a way to create a unique constraint through the SQL Server Management Studio?

How can I create a unique constraint on my column (SQL Server 2008 R2)?

I&#39;m trying to populate a SQL table with a list of words. The table itself it pretty simple:


    CREATE TABLE WORDS(
      ID BIGINT AUTO_INCREMENT, 
      WORD VARCHAR(128) NOT NULL UNIQUE, 
      PRIMARY KEY(ID)
    );

The problem I&#39;m running into is this: when I do the following inserts back to back

    INSERT INTO WORDS(WORD) VALUES(&#39;Seth&#39;);
    INSERT INTO WORDS(WORD) VALUES(&#39;seth&#39;);

The second insert fails with a constraint violation (&quot;Duplicate entry &#39;seth&#39; for key &#39;WORD&#39;&quot;).

How can I get the `UNIQUE` constraint on `WORD` to be case sensitive?

SQL unique varchar case sensitivity question

I need to catch violation of `UNIQUE` constraints in a special way by a C# application I am developing. Is it safe to assume that `Error 2627` will always correspond to a violation of this kind, so that I can use 

    if (ThisSqlException.Number == 2627)
    {
        // Handle unique constraint violation.
    }
    else
    {
        // Handle the remaing errors.
    }

?

Unique Key Violation in SQL Server - Is it safe to assume Error 2627?

Suppose a simple Grails domain class:

    class Account {
        String countryId;

        String userName;

        String password;

        static constraints = {
            ...???...
        }
    }

It is required that user names are unique for a particular &lt;i&gt;countryId&lt;/i&gt;, thus there must be a &lt;i&gt;unique&lt;/i&gt; contraint on two columns. How to express this in the &lt;i&gt;constraints&lt;/i&gt; definition? 

Grails domain class: unique constraint for multiple columns

I&#39;m following up in regards to a [question that I asked earlier][1] in which I sought to seek a conversion from a goofy/poorly written mysql query to postgresql. I believe I succeeded with that. Anyways, I&#39;m using data that was manually moved from a mysql database to a postgres database. I&#39;m using a query that looks like so:

      UPDATE krypdos_coderound cru

      set is_correct = case 
          when t.kv_values1 = t.kv_values2 then True 
          else False 
          end

      from 
      
      (select cr.id, 
        array_agg(
        case when kv1.code_round_id = cr.id 
        then kv1.option_id 
        else null end 
        ) as kv_values1,

        array_agg(
        case when kv2.code_round_id = cr_m.id 
        then kv2.option_id 
        else null end 
        ) as kv_values2

        from krypdos_coderound cr
         join krypdos_value kv1 on kv1.code_round_id = cr.id
         join krypdos_coderound cr_m 
           on cr_m.object_id=cr.object_id 
           and cr_m.content_type_id =cr.content_type_id 
         join krypdos_value kv2 on kv2.code_round_id = cr_m.id

       WHERE
         cr.is_master= False
         AND cr_m.is_master= True 
         AND cr.object_id=%s 
         AND cr.content_type_id=%s 

       GROUP BY cr.id  
      ) t

    where t.id = cru.id
        &quot;&quot;&quot; % ( self.object_id, self.content_type.id)
      )

I have reason to believe that this works well. However, this has lead to a new issue. When trying to submit, I get an error from django that states:

    IntegrityError at (some url): 
    duplicate key value violates unique constraint &quot;krypdos_value_pkey&quot;

I&#39;ve looked at several of the responses posted on here and I haven&#39;t quite found the solution to my problem (although the related questions have made for some interesting reading). I see this in my logs, which is interesting because I never explicitly call insert- django must handle it:


       STATEMENT:  INSERT INTO &quot;krypdos_value&quot; (&quot;code_round_id&quot;, &quot;variable_id&quot;, &quot;option_id&quot;, &quot;confidence&quot;, &quot;freetext&quot;)
       VALUES (1105935, 11, 55, NULL, E&#39;&#39;) 
       RETURNING &quot;krypdos_value&quot;.&quot;id&quot;

However, trying to run that results in the duplicate key error. The actual error is thrown in the code below.

     # Delete current coding         CodeRound.objects.filter(object_id=o.id,content_type=object_type,is_master=True).delete()
      code_round = CodeRound(object_id=o.id,content_type=object_type,coded_by=request.user,comments=request.POST.get(&#39;_comments&#39;,None),is_master=True)
      code_round.save()
      for key in request.POST.keys():
        if key[0] != &#39;_&#39; or key != &#39;csrfmiddlewaretoken&#39;:
          options = request.POST.getlist(key)
          for option in options:
            Value(code_round=code_round,variable_id=key,option_id=option,confidence=request.POST.get(&#39;_confidence_&#39;+key, None)).save()  #This is where it dies
      # Resave to set is_correct
      code_round.save()
      o.status = &#39;3&#39; 
      o.save(

I&#39;ve checked the sequences and such and they seem to be in order. At this point I&#39;m not sure what to do- I assume it&#39;s something on django&#39;s end but I&#39;m not sure. Any feedback would be much appreciated!

  [1]: https://stackoverflow.com/questions/11000068/changing-a-weird-mysql-query-to-postgresql-that-uses-group-concat

Content Type	Original Author	Original Content on Stackoverflow
Question	Lothar	View Question on Stackoverflow
Solution 1 - Mysql	WuHoUnited	View Answer on Stackoverflow
Solution 2 - Mysql	Muhammad Rizwan Kaim Khani	View Answer on Stackoverflow
Solution 3 - Mysql	ypercubeᵀᴹ	View Answer on Stackoverflow
Solution 4 - Mysql	Zulan	View Answer on Stackoverflow
Solution 5 - Mysql	MKA	View Answer on Stackoverflow
Solution 6 - Mysql	user3772326	View Answer on Stackoverflow
Solution 7 - Mysql	KARTHIKEYAN.A	View Answer on Stackoverflow

MySQL - Make an existing Field Unique

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

Solution 4 - Mysql

Solution 5 - Mysql

Solution 6 - Mysql

Solution 7 - Mysql

Ruby on Rails production log rotation

How to get root access on Android emulator?

Attributions