Selecting A row range from a query of queries

问题

How would I select a specific range of rows using a query of queries?

e.g

<cfquery name="myQuery" maxrows ="20" startrow="12">
 SELECT *
 FROM   previous_query
 WHERE  row_numer >= 12
</cfquery>

that sort of thing...

回答1:

This was a tricky one but your problem intrigued me. I think I may have a solution

I wrote a function that delete everything prior to the rows you want and then deletes everything after the rows you want.

the function rowrange() takes 3 parameters. 1. the queryname you are working with. 2. the starting row you want 3. the number of rows you want.

UPDATED: My friend John Whish pointed out that I actually do not need to do the looping to get this to work. Removing the loops makes this much more scalable.

<cfquery name="myQuery">
 SELECT *
 FROM   previous_query
 WHERE  row_numer >= 12
</cfquery>


<cfset  rowRange(myQuery,7,4)>
<cfdump var="#myQuery#">

<cffunction name="rowRange" hint="return a range of rows from a given query">
    <cfargument name="qObj" type="query" required="true">
    <cfargument name="start" type="numeric" required="true" default="1" hint="The number of the first row to include">
    <cfargument name="range" type="numeric" required="true" default="1" hint="The number of rows">


    <cfset var i = arguments.start+arguments.range-1>
    <cfset arguments.qObj.removeRows(i,arguments.qObj.recordcount-i)>
    <cfset arguments.qObj.removeRows(0,arguments.start-1)>

    <cfreturn arguments.qObj>
</cffunction>

回答2:

Doing this natively in CF isn't supported, so you'll have to add a column in your original record set to do the counting for you.

SELECT ..., row_num AS Counter

Row_Num may vary based on your DBMS.

来源：https://stackoverflow.com/questions/11436148/selecting-a-row-range-from-a-query-of-queries

标签

coldfusion

cfquery