Braden Walker

queries.sql

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+PRAGMA foreign_keys = ON;
+
+CREATE TABLE organization (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name VARCHAR(128)
+);
+
+CREATE TABLE channel (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name VARCHAR(128),
+    organization_id INTEGER REFERENCES organization(id)
+);
+
+CREATE TABLE user (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    name VARCHAR(64)
+);
+
+CREATE TABLE channel_user (
+    id INTEGER PRIMARY KEY AUTOINCREMENT, --included so messages can only be posted to the correct channel/user combo
+    channel_id INTEGER REFERENCES channel(id),
+    user_id INTEGER REFERENCES user(id) --might need ON DELETE CASCADE
+);
+
+CREATE TABLE message (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    content TEXT,
+    post_time TIMESTAMP default CURRENT_TIMESTAMP,
+    channel_user_id INTEGER REFERENCES channel_user(id) --might need ON DELETE CASCADE
+);
+
+
+INSERT INTO organization (name) VALUES ("Lambda School");
+
+INSERT INTO channel (name, organization_id) VALUES ("#general", 1);
+INSERT INTO channel (name, organization_id) VALUES ("#random", 1);
+
+INSERT INTO user (name) VALUES ("Alice");
+INSERT INTO user (name) VALUES ("Bob");
+INSERT INTO user (name) VALUES ("Chris");
+
+INSERT INTO channel_user (channel_id, user_id) VALUES (1,1); --Alice in #general
+INSERT INTO channel_user (channel_id, user_id) VALUES (1,2); --Bob in #general
+INSERT INTO channel_user (channel_id, user_id) VALUES (2,1); --Alice in #random
+INSERT INTO channel_user (channel_id, user_id) VALUES (2,3); --Chris in #random
+
+INSERT INTO message (content, channel_user_id) VALUES ("This is Alice posting in #general", 1);
+INSERT INTO message (content, channel_user_id) VALUES ("Once again, Alice posting in #general", 1);
+INSERT INTO message (content, channel_user_id) VALUES ("For the last time, Alice posting in #general", 1);
+INSERT INTO message (content, channel_user_id) VALUES ("This is Bob posting in #general", 2);
+INSERT INTO message (content, channel_user_id) VALUES ("Once again, Bob posting in #general", 2);
+INSERT INTO message (content, channel_user_id) VALUES ("For the last time, Bob posting in #general", 2);
+INSERT INTO message (content, channel_user_id) VALUES ("This is Alice posting in #random", 3);
+INSERT INTO message (content, channel_user_id) VALUES ("Once again, Alice posting in #random", 3);
+INSERT INTO message (content, channel_user_id) VALUES ("This is Chris posting in #random", 4);
+INSERT INTO message (content, channel_user_id) VALUES ("Once again, Chris posting in #random", 4);
+
+
+-- List all organization names
+SELECT * FROM organization;
+
+-- List all channel names
+SELECT * FROM channel;
+
+-- List all channels in a specific organization by name
+SELECT channel.name, organization.name 
+FROM organization, channel 
+WHERE channel.organization_id = organization.id 
+AND organization.name = "Lambda School";
+
+-- List all messages in a specific channel by channel name #general in order of post_time, descending
+SELECT message.content, message.post_time, channel.name 
+FROM message, channel, user, channel_user 
+WHERE message.channel_user_id = channel_user.id 
+AND channel_user.channel_id = channel.id 
+AND channel_user.user_id = user.id 
+AND channel.name = "#general" 
+ORDER BY post_time DESC;
+
+-- List all channels to which user Alice belongs
+SELECT channel.* 
+FROM channel, user, channel_user 
+WHERE channel_user.channel_id = channel.id 
+AND channel_user.user_id = user.id 
+AND user.name = "Alice";
+
+-- List all users that belong to channel #general
+SELECT user.* 
+FROM channel, user, channel_user 
+WHERE channel_user.channel_id = channel.id 
+AND channel_user.user_id = user.id 
+AND channel.name = "#general";
+
+-- List all messages in all channels by user Alice
+SELECT message.*, channel.name 
+FROM message, channel, user, channel_user 
+WHERE message.channel_user_id = channel_user.id 
+AND channel_user.channel_id = channel.id 
+AND channel_user.user_id = user.id 
+AND user.name = "Alice";
+
+-- List all messages in #random by user Bob
+SELECT message.*, channel.name 
+FROM message, channel, user, channel_user 
+WHERE message.channel_user_id = channel_user.id 
+AND channel_user.channel_id = channel.id 
+AND channel_user.user_id = user.id 
+AND user.name = "Bob" 
+AND channel.name= "#random";
+
+-- List the count of messages across all channels per user
+SELECT user.name AS "User Name", COUNT(*) AS "Message Count" 
+FROM message, channel, user, channel_user 
+WHERE message.channel_user_id = channel_user.id 
+AND channel_user.channel_id = channel.id 
+AND channel_user.user_id = user.id 
+GROUP BY user_id 
+ORDER BY user.name DESC;
+
+-- [STRETCH!] List the count of messages per user per channel
+SELECT user.name AS "User Name", channel.name AS "Channel", COUNT(*) AS "Message Count" 
+FROM message, channel, user, channel_user 
+WHERE message.channel_user_id = channel_user.id 
+AND channel_user.channel_id = channel.id 
+AND channel_user.user_id = user.id 
+GROUP BY channel_user.id ;
+
+
+-- Question: What SQL keywords or concept would you use if you wanted to automatically delete all 
+-- messages by a user if that user were deleted from the user table?
+
+-- Answer: Add `ON DELETE CASCADE` to the end of the `message.channel_user` and `channel_user.user_id` line