MySQL内部连接/左连接

Question

I have the following MySQL statement

SELECT * FROM node
        LEFT JOIN field_data_field_featured ON field_data_field_featured.entity_id = node.nid 
        LEFT JOIN field_data_field_mobile_only ON field_data_field_mobile_only.entity_id = node.nid AND field_data_field_mobile_only.field_mobile_only_value = 1
        INNER JOIN field_data_field_related_show ON field_data_field_related_show.entity_id = node.nid 
        WHERE node.status = '1' AND (node.type IN ('game','video','post')) 
        AND field_related_show_nid = 64
        ORDER BY field_featured_value DESC, node.created DESC

It currently returns all records that fit the conditions stated but I would like to add a conditional statement where if field type is a game I would only like to include the record in the result set if the field field_mobile_only_value is 1.

A sample record of the current SQL looks like this

      nid: 351
                    vid: 351
                   type: game
               language: und
                  title: Avalanche at Plankton's Peak
                    uid: 53
                 status: 1
                created: 1403730218
                changed: 1403730218
                comment: 0
                promote: 1
                 sticky: 0
                   tnid: 0
              translate: 0
            entity_type: node
                 bundle: game
                deleted: 0
              entity_id: 351
            revision_id: 351
               language: und
                  delta: 0
   field_featured_value: 0
            entity_type: NULL
                 bundle: NULL
                deleted: NULL
              entity_id: NULL
            revision_id: NULL
               language: NULL
                  delta: NULL
field_mobile_only_value: NULL
            entity_type: node
                 bundle: game
                deleted: 0
              entity_id: 351
            revision_id: 351
               language: und
                  delta: 0
 field_related_show_nid: 64

Answer 1

I don't think you can add a column to the result based on the value of another column in your select query.

Why don't you verify this in your php code?

If it is not a game, just ignore the field_mobile_only_value column.

Answer 2

You could add something like this to the WHERE clause:

AND ( ( node.type = 'game' 
      AND field_data_field_mobile_only.field_mobile_only_value = 1 
      )
    OR node.type <> 'game'
    )

(We can use the inequality operator here, without a concern for NULL values, because a previous predicate has already guaranteed that the values of node.type will not be NULL.)

If type is 'game' , then we only return the row if is equal to 1 .

Otherwise, if type is something other than game , we allow the row to be returned.

In the more general case, where we would want to also return rows that had NULL values for type , a slight modification using the null-safe comparator:

AND ( ( node.type = 'game'
      AND field_data_field_mobile_only.field_mobile_only_value = 1
      )
    OR NOT ( node.type <=> 'game' )
    )

would give an equivalent result.