需要帮助将此SQL查询简化为可能的单个SELECT:
(SELECT * FROM `deals`
WHERE category_id = 1
ORDER BY id desc
LIMIT 10)
UNION
(SELECT * FROM `deals`
WHERE category_id = 2
ORDER BY id desc
LIMIT 10)
UNION
(SELECT * FROM `deals`
WHERE category_id = 4
ORDER BY id desc
LIMIT 10)
UNION
(SELECT * FROM `deals`
WHERE category_i
如何在查询的SELECT子句中增加“固定”值,从而使每一行具有不同的值集?对于一个明显不起作用的示例,说明了它的意图:
SELECT
name, ++x as ordinal
FROM
foo;
name | ordinal
----------------
john | 0
paul | 1
george | 2
ringo | 3
最终目的是从数据库中选择用户,以赢得第一、第二和第三等奖。我会让一名用户获得一等奖,五名二等奖得主和二十三名三等奖得主:
SELECT
name, IF(++x<2, 'first', IF(x&l
我有一个3列的表: list_num、sales_price和days_on_market
我想要运行一个查询,它将为列“days_on_market”的平均值输出一个数字,在按‘sales’排序时,删除前5%和底部5%的行。
我找到了一个例子,我认为在这里会有帮助,但答案太复杂,我无法理解(我刚刚开始学习mySQL上周)。参见下面的示例。
这是我的代码:
SELECT round(avg(days_on_market),0) as "90% Sell In"
FROM sold_q3_2016
WHERE list_num NOT IN (
SELECT list_n
我对数据库中的一个表有两个查询,唯一的区别是限制。我喜欢输出,但我知道一定有更实际的方法来做这件事。有没有人能提个建议?
$sql1 = mysql_query("SELECT * FROM products ORDER BY id DESC LIMIT 20");
$count = mysql_num_rows($sql1);
if ($count > 0) {
while($row = mysql_fetch_array($sql1)){
}
}
$sql2 = mysql_query("SELECT * FROM products ORDER B
我的菜单有以下PHP代码,它可以选择MySQL中的所有链接和名称:
<?php
$url = '';
//select all the top row items
$sql="SELECT * from website_menu where parent_top = '' and parent = '' order by menu_order ASC ";
$rs=mysql_query($sql,$conn) or die(mysql_error());
while($result=mysql_fetch_array($r
下面是我的sql代码与php的结合。
$query = sprintf("SELECT SUM( value ) AS totalvalue
FROM (
SELECT *
FROM answers
WHERE user_id='%s'
AND test_id ='%s'
ORDER BY answers.id DESC
LIMIT
我读到过在大型数据库上使用ORDER BY RAND()运行SQL查询不是一个好主意。
所以这是我破解代码的办法。代码需要从数据库中选择10个随机ids,然后执行第二次select来获取随机行。
$sql = "SELECT id FROM table WHERE image != ''
ORDER BY id DESC LIMIT 50;";
$result = mysql_query($sql);
while($row = mysql_fetch_array($result))
{
foreach($row as $key =&
如何在yii2中按同一列订购两次?
select * from (
select * from your_table order by id desc limit 20)
tmp order by tmp.id asc
为什么我要分类两次?我有活动桌。我想显示它的eventDate比今天大的事件,然后使用asc对其进行排序。
$events = Events::find()->where(['>=', 'eventDate', $today])->andWhere(['status' => 1])->orde