Php 如何将这两个查询合并为一个查询？

使用UNION ALL使其成为单个查询：

$a = mysql_query("SELECT COUNT(*) as `count_1` FROM `table_1` WHERE `this_1` = '1'");
$b = mysql_fetch_assoc($a);

$c = mysql_query("SELECT COUNT(*) as `count_2` FROM `table_1` WHERE `this_2` = '1'");
$d = mysql_fetch_assoc($c);

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您可以使用计数内的条件来计算发生次数。这样，您将得到一行多列：

$a = mysql_query("...the complete query from above...");

$a = mysql_query("...the complete query from above...");

SELECT COUNT(this_1 = '1' OR NULL) AS count_1, COUNT(this_2 = '1' OR NULL) AS count_2