Retrieving a row, with data from key-value pair table in MySQL

Question

I have two tables, one called customer and one called customer_attributes.

The idea is that the customer table holds core customer data, an

Answer 1

Try this:

SELECT `customer`.*, `ca1`.`value1` AS `wedding_date`, `ca2`.`value1` AS `test` 
FROM `customer` 
LEFT JOIN `customer_attributes` AS `ca1` ON customer.customerID = ca1.customerID  AND ca1.key1='wedding_date'
LEFT JOIN `customer_attributes` AS `ca2` ON customer.customerID = ca2.customerID AND ca2.key1='test'
WHERE (customer.customerID = '58029') 

Moving the 2 WHERE conditions on ca1/ca2 into the JOIN condition instead should sort it

Answer 2

The the "key" tests in with the LEFT OUTER JOIN predicates, as such:

SELECT `customer`.*, `ca1`.`value1` AS `wedding_date`, `ca2`.`value1` AS `test` 
FROM `customer` 
LEFT JOIN `customer_attributes` AS `ca1` ON customer.customerID = ca1.customerID 
   AND (ca1.key1 = 'wedding_date') 
LEFT JOIN `customer_attributes` AS `ca2` ON customer.customerID = ca2.customerID 
   AND (ca2.key1 = 'test')
WHERE (customer.customerID = '58029') 

Answer 3

The reason rows are only returned is because of the tests in the WHERE clause. Any rows that do not have the correct key1 are ignored altogether - negating your LEFT JOIN.

You could move the key1 tests to your JOIN conditions

SELECT `customer`.*, `ca1`.`value1` AS `wedding_date`, `ca2`.`value1` AS `test` 
FROM `customer` 
LEFT JOIN `customer_attributes` AS `ca1` ON customer.customerID = ca1.customerID AND ca1.key1 = 'wedding_date'
LEFT JOIN `customer_attributes` AS `ca2` ON customer.customerID = ca2.customerID AND ca2.key1 = 'test'
WHERE (customer.customerID = '58029')