Select in two MySQL tables

In this tutorial you can learn how to select data from two MySQL tables with a single query.
When the SQL query selects columns from diferent tables, you must specify the table name and the column; the syntax is:

SELECT `table1`.`column`, `table2`.`column` FROM `table1`, `table2` WHERE conditon

Let's see some examples, in which we'll use the following two tables, named "categories" and "links".

categories
id	category
1	PHP-MySQL
2	HTML

links
id	link	visits
1	coursesweb.net/php-mysql/arrays	12
1	coursesweb.net/php-mysql/strings	15
2	coursesweb.net/html/html-tables	18

1. Select all the columns from "categories" table where id=2, and the "link" and "visits" columns where visits>13.

SELECT `categories`.*, `links`.`link`, `links`.`visits` FROM `categories`, `links` WHERE `categories`.`id`=2 AND `links`.`visits`>13

Result:

| id | category |                link             | visits |
-----------------------------------------------------------------
| 2 |   HTML    | coursesweb.net/php-mysql/strings |   15   |
| 2 |   HTML    | coursesweb.net/html/html-tables  |   18   |

2. Select the "category", and the "link" columns, where the 'id' in the 'categories' table is 1 and the id in the 'links' table is equal with the 'id' of the 'categories'.

SELECT `categories`.`category`, `links`.`link` FROM `categories`, `links` WHERE `categories`.`id`=1 AND `categories`.`id`=`links`.`id`

Result:

| category  |               link                   |
----------------------------------------------------
| PHP-MySQL | coursesweb.net/php-mysql/arrays  |
| PHP-MySQL | coursesweb.net/php-mysql/strings |

Two Selects in a Query

You can also perform two select commands in a SQL query.
Examples:

1. Select the "link" column (from 'links') where the "id" corresponds to the HTML value (stored in the 'categories').

SELECT `link` FROM `links` WHERE `id`=(SELECT `id` FROM `categories` WHERE `category`='HTML')

Result:

|               link                  |
---------------------------------------
| coursesweb.net/html/html-tables |

2. Counts all rows in the 'links' table, where visits>14, and selects "category" column from 'categories' where id<4.

SELECT (SELECT COUNT(*) FROM `links` WHERE `visits`>14) AS nrl, `category` FROM `categories` WHERE `id`<4

Result:

| nrl | category  |
-------------------
|  2  | PHP-MySQL |
|  2  |   HTML    |

- There is also another way to select columns from two tables in a single query, by using the JOIN command. This method is presented in the next tutorial.

<<-Count the number of .. -- MySQL INNER JOIN, LEFT ..->>

Daily Test with Code Example

HTML

CSS

JavaScript

PHP-MySQL

Which HTML5 tag can be used to embed an external application (SWF, PDF) in web page?

<embed src="flash_game.swf" width="450" height="350" />

Which CSS pseudo-element adds a special style to the first line of a text?

:first-letter :before :first-line

#id:first-line {
  font-weight: bold;
  color: blue;
}

Click on the window object property which gets or sets the URL of current page.

window.location window.self window.status

var url = window.location;
alert(url);

Indicate the PHP function used to get the contents of a file or page and store it into a string.

fopen() file_put_contents() file_get_contents()

$homepage = file_get_contents("http://coursesweb.net/");
echo $homepage;

Select in two MySQL tables

Php-mysql Course

Two Selects in a Query

Daily Test with Code Example

HTML

CSS

JavaScript

PHP-MySQL

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