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What follows is a list of some very useful MySQL queries for use in projects, enjoy. I won’t go into detail how and why they work, I’ll leave that up to you

/*** select records from the previous day ***/
SELECT * FROM users WHERE TO_DAYS(last_login) = ( TO_DAYS(NOW()) - 1 )

/*** select records from last 90 minutes ***/
SELECT* FROM users DATE_SUB(NOW(),INTERVAL 90 MINUTE);

/*** select records from last 1hr 5 mins ***/
SELECT DATE_ADD('1970-01-01 12:00:00', INTERVAL CAST(6/4 AS DECIMAL(3,1)) HOUR_MINUTE);

/*** select records from last hour ***/
select DATE_SUB(NOW(), INTERVAL 1 HOUR);

/*** using the SIGN function to mark a number as positive, negative or null ***/
SELECT backlist, SIGN(backlist) AS user_to_backlist
FROM users
WHERE user_banned IS NOT NULL;

/*** select records from last week ***/
select DATE_SUB(NOW(), INTERVAL 1 WEEK);

/*** get the last day of next month ***/
SELECT LAST_DAY('2006-03-06' + INTERVAL 1 MONTH) AS last_day;

/*** select unique records only ***/
SELECT user_name FROM users GROUP BY users HAVING ( COUNT(user_name) = 1 );

/*** select records from one table that are in another table i.e. all the customers that have placed an order ***/
SELECT DISTINCT cust.customer_id, cust.customer_name
FROM cust INNER JOIN orders ON cust.customer_id = orders.customer_id;

/*** insert data from one table into another ***/
INSERT INTO customers(customer_id, customer_name)
SELECT cus_key, cus_name
FROM customers_2 WHERE customer_name LIKE 'W%';

/*** update information based upon a seperate table ***/
UPDATE cust SET status = '1'
FROM orders WHERE orderdate > '2009-01-01' and orders.customer_id = cus.customer_id;

/*** classic self join example - who is an emoployees manager ***/
SELECT emp.empID, emp.Name, emp.Salary, managers.Name AS manager_name
FROM emp
LEFT JOIN emp AS manager_name
ON emp.ManagerID = Manager.EmployeeID
WHERE (emp.empID= '123456');

/*** using UNION to combine results from multiple queries into a single table ***/
SELECT users.name
FROM users WHERE (users.name BETWEEN 'A%' AND 'M%')
UNION
SELECT banned_users.name FROM banned_users
WHERE (banned_users.name BETWEEN 'A%' AND 'M%');

/*** concatenate column data into a single column ***/
SELECT CONCAT(emp.firstname, '-', emp.lastname) AS emp_full_name FROM emp;

/*** select count of records for each hour ***/
SELECT HOUR(last_login) AS last_login_hour, COUNT(*) AS the_count FROM users GROUP BY HOUR(last_login);

/*** import a csv file ***/
LOAD DATA INFILE '/path/xxx.csv' INTO users_table csv_test_table FIELDS TERMINATED BY ',' LINES TERMINATED BY "\n" (user_name, access_level , user_email);

/*** display current mysql user ***/
SELECT USER();