在一個SQL查詢中選擇最大值和最小值

Question

我有一個表，該表帶有其時間戳記。 現在我需要獲取最早的記錄和最新的記錄

9/10/2014 6:54
9/10/2014 6:53
9/10/2014 6:51
9/8/2014 8:09
9/8/2014 7:00
9/5/2014 7:38
9/5/2014 3:57
9/5/2014 3:51
9/4/2014 11:09
9/4/2014 8:39

目前，這是我通過發送兩個數據庫調用來獲取它們的方法，這會減慢處理速度

$new_timestamp = mysql_query("SELECT TIMESTAMP FROM $rectable ORDER BY TIMESTAMP DESC LIMIT 1");
$col_old = mysql_fetch_assoc($new_timestamp);
$old = $col_new['TIMESTAMP'];

$new_timestamp1 = mysql_query("SELECT TIMESTAMP FROM $rectable ORDER BY TIMESTAMP ASC LIMIT 1");
$col_new = mysql_fetch_assoc($new_timestamp1);
$new = $col_new['TIMESTAMP'];

有什么方法可以優化此代碼和完全填充需求，而無需通過特殊查詢或存儲過程發送兩個數據庫調用

Answer 1

您可以使用max和min獲取最新和最舊的時間戳記

select max(timestamp), min(timestamp) from mytable

Answer 2

與UNION嘗試

select TIMESTAMP as old FROM $rectracktable ORDER BY TIMESTAMP DESC LIMIT 1
union all
select TIMESTAMP as new FROM $rectable ORDER BY TIMESTAMP ASC LIMIT 1