You probably want to use a [`CASE` expression][1].

They look like this:

    SELECT col1, col2, (case when (action = 2 and state = 0) 
     THEN
          1 
     ELSE
          0 
     END)
     as state from tbl1;


  [1]: http://dev.mysql.com/doc/refman/5.0/en/control-flow-functions.html#operator_case

you must write it in SQL not it C/PHP style

    IF( action = 2 AND state = 0, 1, 0 ) AS state

for use in query

    IF ( action = 2 AND state = 0 ) THEN SET state = 1

for use in stored procedures or functions

You&#39;re looking for `case`:

    case when action = 2 and state = 0 then 1 else 0 end as state

MySQL has an `if` syntax (`if(action=2 and state=0, 1, 0)`), but `case` is more universal.

Note that the `as state` there is just aliasing the column. I&#39;m assuming this is in the column list of your SQL query.

    SELECT col1, col2, IF( action = 2 AND state = 0, 1, 0 ) AS state from tbl1;

OR 

    SELECT col1, col2, (case when (action = 2 and state = 0) then 1 else 0 end) as state from tbl1;

both results will same....

according to the mySQL reference manual  this the syntax of using if and else statement : 

&gt;     IF search_condition THEN statement_list
&gt;     [ELSEIF search_condition THEN statement_list] ...
&gt;     [ELSE statement_list]
&gt;     END IF

So regarding your query : 

    x = IF((action=2)&amp;&amp;(state=0),1,2);

or you can use 

    IF ((action=2)&amp;&amp;(state=0)) then 
    state = 1;
    ELSE 
    state = 2;
    END IF;

There is good example in this link : 
http://easysolutionweb.com/sql-pl-sql/how-to-use-if-and-else-in-mysql/

I have a table like this:

    create table1 (field1 int,
                   field2 int default 5557,
                   field3 int default 1337, 
                   field4 int default 1337)

I want to insert a row which has the default values for field2 and field4.

I&#39;ve tried `insert into table1 values (5,null,10,null)` but it doesn&#39;t work and `ISNULL(field2,default)` doesn&#39;t work either.

How can I tell the database to use the default value for the column when I insert a row?

How to insert default values in SQL table?

I am using DictWriter to output data in a dictionary to a csv file.  Why does the CSV file have a blank line in between each data line?  It&#39;s not a huge deal, but my dataset is big and doesn&#39;t fit into one csv file because it has too many lines since the &quot;double-spacing&quot; doubles the number of lines in the file.

My code for writing to the dictionary is:

    headers=[&#39;id&#39;, &#39;year&#39;, &#39;activity&#39;, &#39;lineitem&#39;, &#39;datum&#39;]
    output = csv.DictWriter(open(&#39;file3.csv&#39;,&#39;w&#39;), delimiter=&#39;,&#39;, fieldnames=headers)
    output.writerow(dict((fn,fn) for fn in headers))
    for row in rows:
        output.writerow(row)

Why does CSV file contain a blank line in between each data line when outputting with Dictwriter in Python

How do I write an IF ELSE statement in a MySQL query? 

Something like this:

    mysql_query(&quot;...(irrelevant code).. IF(action==2&amp;&amp;state==0){state=1}&quot;);

Then down in my array I should be able to do this:
              
     $row[&#39;state&#39;] 
    //this should equal 1, the query should not change anything in the database, 
    //just the variable for returning the information

How do write IF ELSE statement in a MySQL query

How do I write an IF ELSE statement in a MySQL query?
Something like this:
<pre><code class="hljs language-scss">mysql_query("...(irrelevant code).. IF(action==2&#x26;&#x26;state==0){state=1}");
</code></pre>
Then down in my array I should be able to do this:
<pre><code class="hljs language-less"> $row['state'] 
//this should equal 1, the query should not change anything in the database, 
//just the variable for returning the information
</code></pre>

    try {
    	$db = new PDO(&quot;mysql:host=&quot;.HOST.&quot;;dbname=&quot;.DB, USER, PW);
    	$st = $db-&gt;prepare(&quot;SELECT * FROM c6ode&quot;);
    }
    catch (PDOException $e){
    	echo $e-&gt;getMessage();
    }

How can I check the mysql error for the query in above case? 

How to view query error in PDO PHP

The title is my question. I googled and try something like

    mysql&gt; !\ clear
    mysql&gt; !\ cls
    mysql&gt; system cls
    mysql&gt; system clear 
    
    blah blah ...

but none of them works.

Anyone show me how to clear screen, just like `cls` command in Windows?


How to clear MySQL screen console in Windows?

I have a case where getting the table name should be from a set variable like: 

    SET @ID_1 = (SELECT ID FROM `slider` LIMIT 0,1);
    SET @Cat = (SELECT Category FROM `slider` LIMIT 0,1);
    select * from @Cat where ID = @ID_1
but doing that way MySQL outputs an error, so could someone show me how I can achieve that, because these are my baby steps in MySQL.

How to select from MySQL where Table name is Variable

Suppose you&#39;re typing a command line query into a MySQL database and you need to cancel out and start over. From a bash shell you could just type ctrl-c and get a new prompt. In MySQL, ctrl-c would exit the client and return you to the shell. 

For example, I have a long, complex SELECT statement typed in but I haven&#39;t yet hit return. I realize that I don&#39;t want to send the command but I want to have the command on-screen so I can use it as a reference. I&#39;d like to bail out without quitting MySQL. Any ideas?

Key point: [the command hasn&#39;t yet been executed][1].


  [1]: https://stackoverflow.com/questions/498344/how-do-i-interupt-a-long-query-in-the-mysql-command-line-tool-without-quitting-m

How do you clear an unexecuted MySQL query from the command line?

My application download mails over IMAP and stores them in a MySQL database. Earlier I was supporting mails size upto 10 MB and hence a &#39;mediumtext&#39; column to store the mail content was enough. Now I need to support mails upto 30MB. So I changed the datatype for the column to &#39;largetext&#39;. Yesterday a mail with size 25 MB was stored. After that whenever I execute mysqldump command it throws error:
&lt;pre&gt;
mysqldump: Error 2020: Got packet bigger than &#39;max_allowed_packet&#39; bytes when dumping table `ib_mailbox_backup` at row: 3369
&lt;/pre&gt;

Row 3369 contains the 25 MB mail.

In MySQL config I increased the &#39;max_allowed_packet&#39; from 64M to 512M and it still fails with the same error. Executing the mysqldump command on the same machine where MySQL server is running. How do I solve this? 

mysqldump error: Got packet bigger than max_allowed_packet&#39;

It&#39;s been clearly put, although opinion none the less, that forgoing curly brackets on a single line `if` statement is not ideal for maintainability and readability.

But what about this?

    if (lemons) { document.write(&quot;foo gave me a bar&quot;); }

It&#39;s even more compressed, and if expanded, the curly brackets won&#39;t be forgotten. Are there any blatant problems, and if not, what are the considerations? I feel like it&#39;s still very readable, at least as much as a ternary operator anyway. It seems to me like ternary operators aren&#39;t suggested as much due to readability, although I feel like that that conclusion isn&#39;t quite as unanimous.

The evil twin in me wants to suggest this, although the syntax obviously isn&#39;t meant for it, and is probably just a bad idea.

    (syntax) ? document.write(&quot;My evil twin emerges&quot;): &quot;&quot;;


JavaScript single line &#39;if&#39; statement - best syntax, this alternative?

I know there is a way for writing a Java `if` statement in short form.

    if (city.getName() != null) {
        name = city.getName();
    } else {
        name=&quot;N/A&quot;;
    }

Does anyone know how to write the short form for the above 5 lines into one line?

Short form for Java if statement

Usually, I use square brackets in the if statement:

    if [ &quot;$name&quot; = &#39;Bob&#39; ]; then ...

But, when I check if `grep` succeeded I don&#39;t use the square brackets:

    if grep -q &quot;$text&quot; $file ; then ...

When are the square brackets necessary in the `if` statement?

When are square brackets required in a Bash if statement?

How do I test a string to see if it contains any of the strings from an array?

Instead of using

    if (string.contains(item1) || string.contains(item2) || string.contains(item3))

Test if a string contains any of the strings from an array

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



Content Type	Original Author	Original Content on Stackoverflow
Question	Dylan Cross	View Question on Stackoverflow
Solution 1 - Mysql	Jack Edmonds	View Answer on Stackoverflow
Solution 2 - Mysql	SergeS	View Answer on Stackoverflow
Solution 3 - Mysql	Eric	View Answer on Stackoverflow
Solution 4 - Mysql	Khandad Niazi	View Answer on Stackoverflow
Solution 5 - Mysql	Dilraj Singh	View Answer on Stackoverflow

How do write IF ELSE statement in a MySQL query

Mysql Problem Overview

Mysql Solutions

Solution 1 - Mysql

Solution 2 - Mysql

Solution 3 - Mysql

Solution 4 - Mysql

Solution 5 - Mysql

Why does CSV file contain a blank line in between each data line when outputting with Dictwriter in Python

How to insert default values in SQL table?

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