Menu
I have this cross-database query...
SELECT `DM_Server`.`Jobs`.*, `DM_Server`.servers.Description AS server, digital_inventory.params, products.products_id, products.products_pdfupload, customers.customers_firstname, customers.customers_lastname FROM `DM_Server`.`Jobs` INNER JOIN `DM_Server`.servers ON servers.ServerID = Jobs.Jobs_ServerID JOIN `cpod_live`.`digital_inventory` ON digital_inventory.jobname = Jobs.Jobs_Name JOIN `cpod_live`.`products` ON products.products_pdfupload = CONCAT(digital_inventory.jobname, ".pdf") JOIN `cpod_live`.`customers` ON customers.customers_id = products.cID ORDER BY `DM_Server`.`Jobs`.Jobs_StartTime DESC LIMIT 50 it runs fine until I make them LEFT JOINs. I thought that by not specifying a type of join it was assumed to be a LEFT JOIN. Is this not the case?
494
LEFT (OUTER) JOIN : Returns all records from the left table, and the matched records from the right table. RIGHT (OUTER) JOIN : Returns all records from the right table, and the matched records from the left table. FULL (OUTER) JOIN : Returns all records when there is a match in either left or right table.
A join combines the set of two tables only. A left join is used when a user wants to extract the left table's data only. Left join not only combines the left table's rows but also the rows that match alongside the right table.
The MySQL LEFT JOIN joins two tables and fetches rows based on a condition, which is matching in both the tables and the unmatched rows will also be available from the table written before the JOIN clause.
A LEFT JOIN is absolutely not faster than an INNER JOIN . In fact, it's slower; by definition, an outer join ( LEFT JOIN or RIGHT JOIN ) has to do all the work of an INNER JOIN plus the extra work of null-extending the results.
I thought that by not specifying a type of join it was assumed to be a LEFT JOIN. Is this not the case?
No, the default join is an INNER JOIN.
Here is a visual explanation of SQL joins.
Inner join
Left join
194
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
