我执行下面的查询 SELECT COUNT(*)
FROM table
WHERE field1='value' AND (field2 >= 1000 OR field3 >= 2000)
有一个指数在FIELD1和其他合成在域2 &场3。 我看到MySQL总是选择field1索引,然后使用其他两个字段进行连接,这是非常糟糕的,因为它需要连接146.000行。 关于如何改进此问题的建议?
我需要获取WHERE子句才能评估某些语句。例如: WHERE field_a = field_b AND
(CASE WHEN <PARAM>type</PARAM> = 5
THEN {field_c = 1 OR field_c = 2}
WHEN <PARAM>type</PARAM> = 6
THEN {field_c = 3 OR field
下面的第一个工作,但是,只是想看看是否有更好的方法... 如果我试图找到所有以'C'开头的记录,标志为2或状态9,我是否需要两次纳入'C'标准? 即 "SELECT * FROM mytable WHERE name like 'C%' AND flag = 2 OR name like 'C%' AND status = 9"
或者说,是有办法更快地写出来,这样我只需要设置“C%”一次呢?
我有一个订单表。状态是在订单加入的泥土订单上。 我只想返回订单,其中加入的soilorder不具有“删除”状态。 我原以为 join sso in db.SoilSamplingOrders on ord.order_id equals sso.order_id
where sso.status.Equals("Removed")!=true
但当时没有记录返回! 感谢您的帮助(以下
$result = mysql_query("SELECT * FROM Volunteers WHERE Volunteers.eventID = " . $var);
$sql = mysql_query("SELECT * FROM Members WHERE Members.pid = " . $temp);
如果发生这种情况,我也会在两个语句的末尾执行或死掉(mysql_erro
嗨,我正在做几个表的联盟。这有点长,但工作! (SELECT user_id,added_date,group_id,'joined',0,0,'' FROM group_members WHERE status = 1)
UNION
(SELECT user_id,added_date,object_id,'made a comment',0,0,'' FROM comments WHERE
我想在我的数据库是这样运行的查询: SELECT SUM(t1.value) AS total1, SUM(t2.value) AS total2, SUM(t3.value) AS total3, SUM(t4.value) AS total4
FROM pay1 t1, pay2 t2, pay3 t3, pay4 t4
WHERE t1.date = '2010-04-29'
AND