通过将两个MySQL查询合并为1来简化两个MySQL查询？

Question

我有两个MySQL查询这是非常相似但它们归到一个特定的WHERE条款（type）一COUNT()，所以我想知道他们是否可以合并成1个查询看到，因为只有WHERE条款（type）differenciates两个？

查询1：

SELECT COUNT(referral_id) AS in_count 
FROM referrals 
WHERE author = '{$author}' 
     AND type = 'in' 
     AND ip_address = '{$ip_address}' 
LIMIT 1 

查询2：

SELECT COUNT(referral_id) AS out_count 
FROM referrals 
WHERE author = '{$author}' 
     AND type = 'out' 
     AND ip_address = '{$ip_address}' 
LIMIT 1 

所有帮助是极大的赞赏：乙

Answer 1

SELECT SUM(IF(type='in',1,0)) as in_count, 
     SUM(IF(type='out',1,0)) as out_count 
FROM referrals 
WHERE author = '{$author}' AND 
     ip_address = '{$ip_address}' 
LIMIT 1 

Answer 2

你只需要一个GROUP BY条款。

SELECT COUNT(referral_id) AS count, type 
FROM referrals 
WHERE author = '{$author}' 
    AND ip_address = '{$ip_address}' 
GROUP BY type 
LIMIT 1