我正在为我的数据库构建通用统计信息。
我想知道如何将这么多的SELECTS联合起来,以便在一行不同的列中得到结果。
SELECT COUNT(*) AS total_users FROM users;
SELECT COUNT(*) AS total_verified FROM users WHERE verified = 1;
SELECT COUNT(*) AS total_passed_tut FROM users WHERE level = 3;
SELECT COUNT(*) AS total_private FROM users WHERE privacy = 0;
SELECT COUNT(*) AS total_friends_only FROM users WHERE privacy = 2;
SELECT COUNT(*) AS total_public FROM users WHERE privacy = 3;
这样做有意义吗?还是应该进行单独的查询并保存到1乘1的数组中?
您可以在一个查询中完成
SELECT COUNT(*) AS total_users,
sum(verified = 1) as total_verified,
sum(level = 3) as total_passed_tut,
sum(privacy = 0) as total_private,
sum(privacy = 2) as total_friends_only,
sum(privacy = 3) as total_public
FROM users;
SELECT (SELECT COUNT(*) AS total_users FROM users) as `total_users`,
SELECT (SELECT COUNT(*) AS total_verified FROM users WHERE verified = 1) as `total_verified`,
SELECT (SELECT COUNT(*) AS total_passed_tut FROM users WHERE level = 3) as `total_passed_tut`,
SELECT (SELECT COUNT(*) AS total_private FROM users WHERE privacy = 0) as `total_private`,
SELECT (SELECT COUNT(*) AS total_friends_only FROM users WHERE privacy = 2) as `total_friends_only`,
SELECT (SELECT COUNT(*) AS total_public FROM users WHERE privacy = 3) as `total_public`
FROM dual