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MySQL 5.7 Reference Manual
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MySQL 5.7 Reference Manual  /  ...  /  Using User-Defined Variables

3.6.5 Using User-Defined Variables

You can employ MySQL user variables to remember results without having to store them in temporary variables in the client. (See Section 9.4, “User-Defined Variables”.)

For example, to find the articles with the highest and lowest price you can do this:

mysql> SELECT @min_price:=MIN(price),@max_price:=MAX(price) FROM shop;
mysql> SELECT * FROM shop WHERE price=@min_price OR price=@max_price;
+---------+--------+-------+
| article | dealer | price |
+---------+--------+-------+
|    0003 | D      |  1.25 |
|    0004 | D      | 19.95 |
+---------+--------+-------+
Note

It is also possible to store the name of a database object such as a table or a column in a user variable and then to use this variable in an SQL statement; however, this requires the use of a prepared statement. See Section 13.5, “Prepared SQL Statement Syntax”, for more information.


User Comments
User comments in this section are, as the name implies, provided by MySQL users. The MySQL documentation team is not responsible for, nor do they endorse, any of the information provided here.
  Posted by Karljürgen Feuerherm on December 22, 2017
Note that the variables are static, not dynamically refreshed, and reflect the highest and lowest values at the time they are set. So if for some reason the highest or lowest value changes between the two SELECT queries, the answer will be incorrect.
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