我正在处理一个 Coldfusion8/MySQL 查询,其中我正在扫描数据库中的 AB 对,例如:
S=2, M=2, L=2, XL=2
我正在尝试改进最初处理此问题的脚本,该脚本将条目限制为 4 对,因为我想知道,为什么它首先选择具有一对匹配的所有记录,然后使用HAVING仅选择所有对匹配的记录.
这是原始查询,之后是我的当前版本:
<!--- placeholders --->
<cfparam name="s01" default="">
<cfparam name="s02" default="">
<cfparam name="s03" default="">
<cfparam name="s04" default="">
<cfparam name="q01" default="">
<cfparam name="q02" default="">
<cfparam name="q03" default="">
<cfparam name="q04" default="">
<!--- check length of user inputs --->
<cfset sizes = ListLen(s_lot_groesse,",")>
<cfset qtys = ListLen(s_lot_menge,",")>
<!--- populate placeholders --->
<cfif sizes gt 0><cfset s01 = trim(ListGetAt(s_lot_groesse, 1,","))></cfif>
<cfif sizes gt 1><cfset s02 = trim(ListGetAt(s_lot_groesse, 2,","))></cfif>
<cfif sizes gt 2><cfset s03 = trim(ListGetAt(s_lot_groesse, 3,","))></cfif>
<cfif sizes gt 3><cfset s4 = trim(ListGetAt(s_lot_groesse, 4,","))></cfif>
<cfif qtys gt 0><cfset q01 = trim(ListGetAt(s_lot_menge, 1,","))></cfif>
<cfif qtys gt 1><cfset q02 = trim(ListGetAt(s_lot_menge, 2,","))></cfif>
<cfif qtys gt 2><cfset q03 = trim(ListGetAt(s_lot_menge, 3,","))></cfif>
<cfif qtys gt 3><cfset q04 = trim(ListGetAt(s_lot_menge, 4,","))></cfif>
<!--- query --->
<cfquery datasource="db" name="lotsuche">
SELECT styleno, count(*) as total_styles
FROM styles
WHERE 1 = 1
AND (
<cfif s01 neq "" AND q01 neq "">(groesse = "#s01#" AND bestand >= "#q01#")</cfif>
<cfif s02 neq "" AND q02 neq "">OR (groesse = "#s02#" AND bestand >= "#q02#")</cfif>
<cfif s03 neq "" AND q03 neq "">OR (groesse = "#s03#" AND bestand >= "#q03#")</cfif>
<cfif s04 neq "" AND q04 neq "">OR (groesse = "#s04#" AND bestand >= "#q04#")</cfif>
)
GROUP BY styleno
HAVING total_styles= "#sizes#"
</cfquery>
新版本:
<!--- build a 2D array --->
<cfscript>
variables.lotArray = ArrayNew(2);
variables.sizeCounter = 1;
variables.qtyCounter = 1;
</cfscript>
<cfloop list="#LOCAL.Search.s_lot_groesse#" delimiters=", " item="size">
<cfscript>
variables.lotArray[variables.lotCounter][1] = size;
variables.lotCounter = variables.lotCounter + 1;
</cfscript>
</cfloop>
<cfloop list="#LOCAL.Search.s_lot_menge#" delimiters=", " item="qty">
<cfscript>
variables.lotArray[variables.qtyCounter][2] = qty;
variables.qtyCounter = variables.qtyCounter + 1;
</cfscript>
</cfloop>
<!--- get array length --->
<cfset variables.lotArrayLen = arrayLen(variables.lotArray)>
<!--- query --->
<cfquery datasource="ds" name="lotsuche">
SELECT art.styleNo, count(*) as total_styles
FROM styles AS art
WHERE 1 = 1
<cfloop from="1" to="#variables.lotArrayLen#" index="i">
AND ( art.groesse = <cfqueryparam cfsqltype="cfsql_varchar" value="#variables.lotArray[i][1]#">
AND art.bestand >= <cfqueryparam cfsqltype="cfsql_varchar" value="#variables.lotArray[i][2]#">
</cfloop>
GROUP BY art.styleno
<!--- HAVING anzahl = "#variables.lotArrayLen#" --->
</cfquery>
问题:
我不明白为什么在原始查询中使用OR和HAVING,因为这不是选择具有一对匹配的所有记录而不是仅选择具有所有对匹配的记录吗?如果要扫描几百万个条目,哪种方法更好/更快?另外,像我一样重新考虑整个事情是否有意义?
感谢帮助!