Why Doesn't My Left Join Return All Rows From the Left Table?

Left Join Not Returning All Rows: Addressing the Issue

As discussed in a previous thread, the absence of all rows in a left join query can stem from an improperly placed WHERE clause. In this case, a query aims to extract data from the 'jos_hp_properties' table and optionally select a value named 'room_price_high' from the 'jos_hp_properties2' table based on the field column being equal to 23.

To resolve this issue and ensure the return of all rows from the first table, the WHERE condition should be relocated from its original position after the LEFT OUTER JOIN statement to within the JOIN clause itself. The modified query should resemble this:

SELECT pr.*, pr7.value AS `room_price_high`
  FROM `jos_hp_properties` pr
       LEFT JOIN `jos_hp_properties2` pr7 
       ON pr7.property=pr.id
   AND 
       pr7.field=23

By incorporating the WHERE condition within the JOIN, the query becomes more explicit and instructs the database to only retrieve rows from the second table where the field column is equal to 23. This ensures that all rows from the first table are returned, regardless of whether a matching value exists in the second table. Consequently, the corresponding NULL values will be returned for rows in the first table that do not have a matching row in the second table based on the field=23 criteria.

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