I have created 2 tables in my SQL. One is the user_info table which stores the time of login and timezone of login for each user. The other is the post_table which stores the postid, user who makes the post, time of post and timezone for each posts.
CREATE TABLE user_info
(
user_id VARCHAR(20),
login_date DATE,
login_time_zone VARCHAR(20),
PRIMARY KEY (user_id)
);
CREATE TABLE post_table
(
post_id VARCHAR(20),
user_id VARCHAR(20),
datepost DATE,
time_zone VARCHAR(20),
PRIMARY KEY (post_id),
FOREIGN KEY (user_id) REFERENCES user_info(user_id) ON DELETE CASCADE
) ;
Some sample data for my tables is as below -
INSERT INTO user_info VALUES( 'u1', to_date('9/17/2009 20:00','MM/DD/YYYY mi:ss'), -2 );
INSERT INTO user_info VALUES( 'u2', to_date('9/17/2009 19:55','MM/DD/YYYY mi:ss'), -4 );
INSERT INTO post_table VALUES( 'p1', 'u1', to_date('9/17/2009 20:50','MM/DD/YYYY mi:ss'), 6 );
INSERT INTO post_table VALUES( 'p2', 'u2', to_date('9/17/2009 20:30','MM/DD/YYYY mi:ss'), -5 );
INSERT INTO post_table VALUES( 'p3', 'u2', to_date('9/18/2009 6:00','MM/DD/YYYY mi:ss'), 2 );
INSERT INTO post_table VALUES( 'p4', 'u1', to_date('9/17/2009 21:00','MM/DD/YYYY mi:ss'), -3 );
I need to write an SQL query which - finds the user(s) whose time difference between the login time and the latest time when he/she writes a post is the smallest. I need to consider the timezones here as well.
I am unsure if time_zone should be of type VARCHAR or TIMESTAMP so have created it as VARCHAR in my tables.
Someone please help me form this query.
PS : How do I user <code> tags in this forum to write sql statements.
Edited by: user11994430 on Oct 9, 2009 5:59 PM