merge two queries with MySQL

Robert Saylor
Robert Saylor used Ask the Experts™
on
Hi, I want to merge 2 queries so I don't have to run query 1 then a nested query 2 with php. How would you merge these two as 1 query?

Query 1:
SELECT
	DISTINCT `contacts`.`contactID`,
	`contacts`.`first`,
	`contacts`.`last`,
	`contacts`.`email`

FROM
	`suspended_inventory` si, `reservations`,`contacts`
WHERE
	`si`.`reservationID` = `reservations`.`reservationID`
	AND `reservations`.`reservation_date` BETWEEN '20110101' AND '20141231'
	AND `si`.`contactID` = `contacts`.`contactID`
	AND `contacts`.`email` != ''
	AND `contacts`.`deceased` != 'Y'
	AND `contacts`.`omit_from_future_mailings` != 'Y'

ORDER BY `contacts`.`contactID`

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I then get a contactID value. In Query 1 I would like to count the number of records returned. If 0 return 0.

Query 2
SELECT
	COUNT(`inventory`.`reservationID`) AS 'total'

FROM
	`inventory`,`reservations`

WHERE
	`inventory`.`passengerID` = '99'
	AND `inventory`.`reservationID` = `reservations`.`reservationID`
	AND `reservations`.`reservation_date` BETWEEN '20110101' AND '20141231'

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I would like to run Query 2 inside Query 1 in the select area returning the value if possible. If not, then I will have to run this as a nested query in php.
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Billing Engineer
Most Valuable Expert 2014
Top Expert 2009
Commented:
something like this should be a starter:

SELECT	`contacts`.`contactID`,
	`contacts`.`first`,
	`contacts`.`last`,
	`contacts`.`email`
  ,  (SELECT COUNT(`inventory`.`reservationID`)
   FROM	`inventory`,`reservations`
  WHERE `inventory`.`passengerID` = '99'
	AND `inventory`.`reservationID` = `reservations`.`reservationID`
	AND `reservations`.`reservation_date` BETWEEN '20110101' AND '20141231'
  )   AS 'total'
FROM
	`suspended_inventory` si, `reservations`,`contacts`
WHERE
	`si`.`reservationID` = `reservations`.`reservationID`
	AND `reservations`.`reservation_date` BETWEEN '20110101' AND '20141231'
	AND `si`.`contactID` = `contacts`.`contactID`
	AND `contacts`.`email` != ''
	AND `contacts`.`deceased` != 'Y'
	AND `contacts`.`omit_from_future_mailings` != 'Y'

ORDER BY `contacts`.`contactID`
                                  

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tip: use aliases in your queries:
http://www.experts-exchange.com/Database/Miscellaneous/A_11135-Why-should-I-use-aliases-in-my-queries.html
Robert SaylorSenior Developer

Author

Commented:
Thanks!

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