Comparison of the two types of SQL statements and comparison of the two types of SQL statements

Comparison of the two types of SQL statements and comparison of the two types of SQL statements
SUM (p. payable-p. single_price) AS profitCount,
M. order_id AS orderId,
M. create_time,
M. dept_airport_code,
M. arrv_airport_code,
M. payable AS price
FROM
Om_passenger p,
Om_order m
WHERE
P. order_id = m. order_id
AND p. ticket_status = '1'
AND m. create_type = 3
AND m. order_status = '20140901'
GROUP
P. order_id
ORDER
M. create_time DESC;

**************************************** **************************
SELECT
SUM (p. payable-p. single_price) AS profitCount,
M. order_id AS orderId,
M. create_time,
M. dept_airport_code,
M. arrv_airport_code,
M. payable AS price
FROM
Om_passenger p,
(
SELECT
*
FROM
Om_order t
WHERE
T. create_type = 3
AND t. order_status = '20140901'
) AS m
WHERE
P. order_id = m. order_id
AND p. ticket_status = '1'
GROUP
M. order_id
ORDER

M. create_time DES

The differences between the two SQL statements are as follows: 1. Join the SQL statement first and then query it in a unified manner; 2. Join the SQL statement after query and then query it at the end. In general, the former one is more efficient, the latter is slower.