我正在创建一个表,然后显示记录。我想显示用户的高度在'英寸'格式,但它会存储在'厘米'格式的用户表。现在我想知道哪种方式会给我更快的结果?
使用加入// to select records
SELECT *.u FROM, h.height_inch user as u join height as h on u.height_cm =h.height_cm
WHERE u.user_id = 2 AND ...;
//for display in php
foreach($all_records AS $key => $val) {
echo $val['height_inch'];
}
OR单用户表(比)快/慢:
// to select records
SELECT * user WHERE u.user_id = 2 AND ...;
//for display in php
foreach($all_records AS $key => $val) {
$height_in_cm = $val['height_inch']
$height_in_inch= convert_to_inch($height_in_cm); //function for convert height cm to inch..
echo $height_in_inch;
}
一个更快的替代方法是简单地在SQL中执行算术,这样您就不必存储固定的转换数据或迭代结果。
SELECT height_cm, height_inches as (height_cm / 2.54) FROM table;