带有count的子查询后插入MYSQL

Question

我正在尝试将一些数据插入到表中，但仅在子查询COUNT为＆gt; 0

这是我到目前为止所做的。

INSERT INTO users_friends (userId, friendId) VALUES (77, 100) 
WHERE 
(SELECT COUNT(id) FROM users WHERE email = 'a@g.com') > 0

两个查询都独立工作。

这应该是一个简单的修复希望。干杯

Answer 1

SQLFiddle demo if there are records 'a@g.com'

SQLFiddle demo if there are NOT records 'a@g.com'

INSERT INTO users_friends (userId, friendId) 
SELECT 77, 100 
FROM users WHERE email = 'a@g.com' LIMIT 1;

另一种方式是：

INSERT INTO users_friends (userId, friendId) 
SELECT 77, 100 
FROM dual
WHERE EXISTS
      ( SELECT * FROM users WHERE email = 'a@g.com' ) ;

Answer 2

试试这个::

INSERT INTO users_friends (userId, friendId) 
(SELECT 77, 100  FROM users GROUP BY email HAVING email= 'a@g.com' and count(id)>0)

Answer 3

INSERT INTO users_friends (userId, friendId) 
SELECT 77, 100 FROM users WHERE email = 'a@g.com'
GROUP BY email
HAVING COUNT(id) > 0