Question

I’m creating a search function. My sql query uses LIKE and OR LIKE in the where clause. One of the fields in the table I’m searching in is called quantity_types where it stores only codes that corresponds to the values found in another table. So to retrieve the values from the other, I want to use a Left Outer Join in my query.

Here’s my sample code:

SELECT * FROM `pharmacy_items`
LEFT OUTER JOIN pharmacy_quantity_types
ON pharmacy_items.quantity_type = pharmacy_quantity_types.id
AND 'pharmacy_items.name' LIKE '%query_here%'
OR 'pharmacy_items.description' LIKE '%query_here%'

This query returns all the records in my pharmacy_items table instead of those records which are supposed to be returned with I’m not using a LEFT OUTER JOIN.

How would I build my query such that the returned results are those that satisfies first the WHERE clause before the LEFT OUTER JOIN

Answer 1

It sounds like you want this:

SELECT *
  FROM pharmacy_items
  LEFT
 OUTER
  JOIN pharmacy_quantity_types
    ON pharmacy_items.quantity_type = pharmacy_quantity_types.id
 WHERE pharmacy_items.name LIKE '%query_here%'
    OR pharmacy_items.description LIKE '%query_here%'

where the restrictions on pharmacy_items records are in a WHERE clause rather than in a LEFT OUTER JOIN‘s ON clause.

(Also note:

• AND has higher precedence than OR, so a AND b OR C means (a AND b) OR c, whereas I think you wanted a AND (b OR C). The above query fixes this implicitly, by moving b OR c into a WHERE clause, so it’s separated from a anyway.
• '...' is a literal string, so 'pharmacy_items.name' means “the actual string pharmacy_items.name“, which is not the same as “the name field of the pharmacy_items record”. The latter is written pharmacy_items.name or `pharmacy_items`.`name`.)

)