![]() ![]() A right outer join works exactly like a left outer join, except it always keeps rows from the right table and fills columns from the left table with NULL when there aren’t matches. The SQL standard defines two other kinds of SQL join types for the outer join, but they are used much less often-so much less than some databases don’t even implement them. What about right outer SQL join and full outer join? If we want to combine information about an order with information about the product that was ordered, we can do an inner join: To match the key, every record in orders has a product ID in the orders.product_id field: that’s a foreign key. For example, every record in the products table has a unique ID in the products.id field: that’s the primary key. We normally join tables by matching the foreign keys in one table to the primary keys in another. Quick review of SQL Join TypesĪ SQL join tells the database to combine columns from different tables. Please note that joins only work with relational databases. If you’re new to the subject you may want to check out the SQL joins article as well. ![]() This article looks at different types of SQL joins. Confusing NULLs in data with NULLs from mis-matches.Using SQL joins on “matches” that aren’t meaningful.Doing an inner SQL join instead of an outer join.What about right outer SQL join and full outer join?.In other words, I want to show sum of rows of separately INNER JOIN between the base table and other tables. | 19 | 1542866579 | 1799477 | NULL | NULL | NULL | NULL |īut I don't want to get the rows that were not exist (NULL) in right-side tables (other 23 tables). | notif_id | da | uft_id | un | tr_n | cm_tx | av_ul | The result of that query is like this: +-+-+-+-+-+-+-+ LEFT JOIN tricks trickComment_tricks ON trickComment_id = trickComment_id LEFT JOIN users trickComment_users ON trickComment_users.u_id = trickComment_userForTricks.u_id On trickComment_userForTricks.uft_id = notif_trick_comment.uft_id LEFT JOIN user_for_tricks trickComment_userForTricks LEFT JOIN notif_trick_comment ON notif_trick_comment.notif_id = notif_dest_user.notif_id LEFT JOIN users like_users ON like_userForTricks.u_id = like_users.u_id LEFT JOIN tricks like_tricks ON like_id = like_id LEFT JOIN user_for_tricks like_userForTricks ON notif_trick_like.uft_id = like_userForTricks.uft_id LEFT JOIN notif_trick_like ON notif_dest_user.notif_id = notif_trick_like.notif_id LEFT JOIN notif_all ON notif_all.notif_id = notif_dest_user.notif_id ![]() My query sample: SELECT notif_dest_user.notif_id,ĬOALESCE(notif_trick_like.uft_id, notif_trick_comment.uft_id) AS uft_id,ĬOALESCE(like_users.un, trickComment_users.un) AS un,ĬOALESCE(like_n, trickComment_n) AS tr_n,ĬOALESCE(trickComment_users.av_ul,like_users.av_ul) AS av_ul But as I want to join one with another tables, I have to use LEFT JOIN. I want to JOIN a base table with another 23 tables. ![]()
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