单个值（getValue）

普通查询

$db = Be::getDb(); 

$sql = 'SELECT name FROM user WHERE id = \'40801a44-9e19-11ec-a3cb-0242ac180065\'';
$name = $db->getValue($sql);

$sql = 'SELECT COUNT(*) FROM user WHERE age<18 AND sex=\'女\'';
$count = $db->getValue($sql);

$sql = 'SELECT MIN(age) FROM user WHERE sex=\'女\'';
$minAge = $db->getValue($sql);

占位符查询

$db = Be::getDb(); 

$sql = 'SELECT COUNT(*) FROM user WHERE age<? AND sex=?';
$count = $db->getValue($sql, [18, '女']);

返回一个值

• 当查询结果有多条时，仅取第一条记录
• 当前询结结有多列时，仅取第一列内容