mysql

问题 I have users with many posts . I want to build an SQL query that would do the following in 1 query (no subquery), and hopefully no unions if possible. I know I can do this with union but I want to learn if this can be done using only joins. I want to get a list of distinct active users who: have no posts have no approved posts Here's what I have so far: SELECT DISTINCT u.* FROM users u LEFT JOIN posts p ON p.user_id = u.id LEFT JOIN posts p2 ON p2.user_id = u.id WHERE u.status = 'active' AND

问题 I have users with many posts . I want to build an SQL query that would do the following in 1 query (no subquery), and hopefully no unions if possible. I know I can do this with union but I want to learn if this can be done using only joins. I want to get a list of distinct active users who: have no posts have no approved posts Here's what I have so far: SELECT DISTINCT u.* FROM users u LEFT JOIN posts p ON p.user_id = u.id LEFT JOIN posts p2 ON p2.user_id = u.id WHERE u.status = 'active' AND

问题 This is my situation: I'm trying to connect to my MySQL database with a PHP file on my Apache server, now: my PHP can connect to the MySQL database when I run it from the terminal (using "php -f file.php" ) but when I execute it from a web page it just doesn't connect. This is my php file: echo "TRY CONNECTION"; $conn = mysql_connect($servername, $username, $password); echo "EXECUTED CONNECTION"; The Linux shell prints this: TRY CONNECTIONEXECUTED CONNECTION But the web page prints this: :TRY

问题 I am using mysql db to save id's. It was working fine. But now an id like this 10000000754987. Is stored as 1.0000000754987E+14. How I can I fix it. The field is set to varchar 255 characters limit. I appreciate any help. Thanks. 回答1: You're apparently using PHP to generate that ID. Since you didn't mention what's exactly happening, I can only assume certain reasons for your database design. First off, you could store that number as bigint and not varchar . It's an integer you're saving, I

问题 I develop mobile social network. All data stored in MySQL (via shards). Hot data stored in Redis, and there is shards map in Redis too. Backend = node.js (express) What is the right way of fast requests to a different MySQL servers within one request to the back-end from mobile client? Example: The client requests the server to the user profile with id = 1, which we store on the server mysql-1 shard #1. At the same moment another client requests the server to the user profile with id = 2,

问题 I develop mobile social network. All data stored in MySQL (via shards). Hot data stored in Redis, and there is shards map in Redis too. Backend = node.js (express) What is the right way of fast requests to a different MySQL servers within one request to the back-end from mobile client? Example: The client requests the server to the user profile with id = 1, which we store on the server mysql-1 shard #1. At the same moment another client requests the server to the user profile with id = 2,

问题 I develop mobile social network. All data stored in MySQL (via shards). Hot data stored in Redis, and there is shards map in Redis too. Backend = node.js (express) What is the right way of fast requests to a different MySQL servers within one request to the back-end from mobile client? Example: The client requests the server to the user profile with id = 1, which we store on the server mysql-1 shard #1. At the same moment another client requests the server to the user profile with id = 2,

问题 I develop mobile social network. All data stored in MySQL (via shards). Hot data stored in Redis, and there is shards map in Redis too. Backend = node.js (express) What is the right way of fast requests to a different MySQL servers within one request to the back-end from mobile client? Example: The client requests the server to the user profile with id = 1, which we store on the server mysql-1 shard #1. At the same moment another client requests the server to the user profile with id = 2,

问题 I develop mobile social network. All data stored in MySQL (via shards). Hot data stored in Redis, and there is shards map in Redis too. Backend = node.js (express) What is the right way of fast requests to a different MySQL servers within one request to the back-end from mobile client? Example: The client requests the server to the user profile with id = 1, which we store on the server mysql-1 shard #1. At the same moment another client requests the server to the user profile with id = 2,