這是四種oracle排序中NULL值處理的方法:
1、使用nvl函數
語法:Nvl(expr1, expr2)
若EXPR1是NULL,則返回EXPR2,否則返回EXPR1.
SELECT NAME,NVL(TO_CHAR(COMM),'NOT APPLICATION') FROM TABLE1;
nvl函數可以在輸入參數爲空時轉換爲一特定值,如
nvl(person_name,“未知”)表示若person_name字段值爲空時返回“未知”,如不爲空則返回person_name的字段值。
通過這個函數可以定製null的排序位置。
2、使用decode函數
decode函數比nvl函數更強大,同樣它也可以將輸入參數爲空時轉換爲一特定值,如
decode(person_name,null,“未知”, person_name)表示當person_name爲空時返回“未知”,如不爲空則返回person_name的字段值。
通過此函數也可以定製null的排序位置。
若Order by 中指定了表達式Nulls first則表示null值的記錄將排在最前(不管是asc 還是 desc)
若Order by 中指定了表達式Nulls last則表示null值的記錄將排在最後 (不管是asc 還是 desc)
將nulls始終放在最前:
select * from tbl order by field nulls first
select * from tbl order by field desc nulls last
Case語法是Oracle 9i後開始支持的,是一個比較靈活的語法,同樣在排序中也可以應用
如:
select *
from students
order by (case person_name
when null then
'未知'
else
person_name
end)
表示在person_name字段值爲空時返回’未知’,如果不爲空則返回person_name
通過case語法同樣可以定製null的排序位置。
!defined('PATH_ADMIN') && exit('Forbidden');
class mod_gcdownload
{
public static function get_gcdownload_datalist($start = 0,$rowsperpage = PAGE_ROWS, $datestart = '',$dateend = '',$ver = '',$coopid = '',$subcoopid = '',$sortfield = '', $sorttype = '', $pid = 123456789, $plat = 'abcdefg'){
$sql = '';
$condition = empty($datestart) ? " WHERE 1=1 " : " WHERE t.statistics_date >= '$datestart' AND t.statistics_date <= '$dateend'";
if($ver)
{
$condition .= " AND t.edition='$ver'";
}
if($coopid)
{
$condition .= " AND t.suco_coopid=$coopid";
}
if($subcoopid)
{
$condition .= " AND t.suco_subcoopid=$subcoopid";
}
if($sortfield && $sorttype){
$condition .= " ORDER BY t.{$sortfield} {$sorttype} NULLS LAST";
}elseif($sortfield){
$condition .= " ORDER BY t.{$sortfield} desc NULLS LAST";
}else{
$condition .= " ORDER BY t.statistics_date desc NULLS LAST";
}
$finish = $start + $rowsperpage;
$joinsqlcollection = "(SELECT tc.coop_name, tsc.suco_name, tsc.suco_coopid,tsc.suco_subcoopid, s.edition, s.new_user, d.one_user, d.three_user, d.seven_user, s.statistics_date FROM (((pdt_stat_newuser_{$pid}_{$plat} s LEFT JOIN pdt_days_dl_remain_{$pid}_{$plat} d ON s.statistics_date=d.new_date AND s.subcoopid=d.subcoopid AND s.edition=d.edition )LEFT JOIN [email protected]@JTINFO tsc ON s.subcoopid=tsc.suco_subcoopid) LEFT JOIN [email protected]@JTINFO tc ON tsc.suco_coopid=tc.coop_id))";
$sql = "SELECT * FROM (SELECT tb_A.*, ROWNUM AS rn FROM (SELECT t.* FROM $joinsqlcollection t {$condition} ) tb_A WHERE ROWNUM <= {$finish} ) tb_B WHERE tb_B.rn>{$start} ";
$countsql = "SELECT COUNT(*) AS totalrows, SUM(t.new_user) AS totalnewusr,SUM(t.one_user) AS totaloneusr,SUM(t.three_user) AS totalthreeusr,SUM(t.seven_user) AS totalsevenusr FROM $joinsqlcollection t {$condition} ";
$db = oralceinit(1);
$stidquery = $db->query($sql,false);
$output = array();
while($row = $db->FetchArray($stidquery, $skip = 0, $maxrows = -1))
{
$output['data'][] = array_change_key_case($row,CASE_LOWER);
}
$count_stidquery = $db->query($countsql,false);
$row = $db->FetchArray($count_stidquery, $skip = 0, $maxrows = -1);
$output['total']= array_change_key_case($row,CASE_LOWER);
//echo "<br />".($sql)."<br />";
return $output;
}
}