I have a table that uses 3 foreign keys into other tables. When I perform a left join, I get duplicate columns. MySQL says that the USING
syntax will reduce the duplicate columns, but there aren't examples for multiple keys.
Given:
mysql> describe recipes;
+------------------+------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+------------------+------+-----+---------+-------+
| ID_Recipe | int(11) | NO | PRI | NULL | |
| Recipe_Title | char(64) | NO | | NULL | |
| Difficulty | int(10) unsigned | NO | | NULL | |
| Elegance | int(10) unsigned | NO | | NULL | |
| Quality | int(10) unsigned | NO | | NULL | |
| Kitchen_Hours | int(10) unsigned | NO | | NULL | |
| Kitchen_Minutes | int(10) unsigned | NO | | NULL | |
| Total_Hours | int(10) unsigned | NO | | NULL | |
| Total_Minutes | int(10) unsigned | NO | | NULL | |
| Serving_Quantity | int(10) unsigned | NO | | NULL | |
| Description | varchar(128) | NO | | NULL | |
| ID_Prep_Text | int(11) | YES | | NULL | |
| ID_Picture | int(11) | YES | | NULL | |
| Category | int(10) unsigned | NO | | NULL | |
| ID_Reference | int(11) | YES | | NULL | |
+------------------+------------------+------+-----+---------+-------+
15 rows in set (0.06 sec)
mysql> describe recipe_prep_texts;
+------------------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+---------------+------+-----+---------+-------+
| ID_Prep_Text | int(11) | NO | PRI | NULL | |
| Preparation_Text | varchar(2048) | NO | | NULL | |
+------------------+---------------+------+-----+---------+-------+
2 rows in set (0.02 sec)
mysql> describe recipe_prep_texts;
+------------------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+---------------+------+-----+---------+-------+
| ID_Prep_Text | int(11) | NO | PRI | NULL | |
| Preparation_Text | varchar(2048) | NO | | NULL | |
+------------------+---------------+------+-----+---------+-------+
2 rows in set (0.02 sec)
mysql> describe mp_references;
+--------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+---------+------+-----+---------+-------+
| ID_Reference | int(11) | NO | PRI | NULL | |
| ID_Title | int(11) | YES | | NULL | |
| ID_Category | int(11) | YES | | NULL | |
+--------------+---------+------+-----+---------+-------+
3 rows in set (0.00 sec)
My query statement:
SELECT *
FROM Recipes
LEFT JOIN (Recipe_Prep_Texts, Recipe_Pictures, mp_References)
ON (
Recipe_Prep_Texts.ID_Prep_Text = Recipes.ID_Prep_Text AND
Recipe_Pictures.ID_Picture = Recipes.ID_Picture AND
mp_References.ID_Reference = Recipes.ID_Reference
);
My objective is to get one row of all the columns from the join without duplicate columns. I'm using MySQL C++ Connector to send the SQL statements and retrieve result sets. I believe that the C++ Connector is having issues with duplicate column names.
So what is the SQL statement syntax that I should use?
Reference to MySQL JOIN syntax
I believe the following should work:
SELECT *
FROM Recipes
LEFT JOIN Recipe_Prep_Texts USING (ID_Prep_Text)
LEFT JOIN Recipe_Pictures USING (ID_Picture)
LEFT JOIN mp_References USING (ID_Reference)
Since it looks like most of the tables you are joining on have a few columns except for the first one, how about:
SELECT Recipes.*,
Recipe_Prep_Texts.Preparation_Text,
Recipe_Pictures.Foo, -- describe is missing in OP
mp_References.ID_Title,
mp_References.ID_Category
FROM Recipes
LEFT JOIN (Recipe_Prep_Texts, Recipe_Pictures, mp_References)
ON (
Recipe_Prep_Texts.ID_Prep_Text = Recipes.ID_Prep_Text AND
Recipe_Pictures.ID_Picture = Recipes.ID_Picture AND
mp_References.ID_Reference = Recipes.ID_Reference
);
I can't tell you how many times I wished I had
SELECT (* - foo) FROM table
especially in cases where foo is some huge field like a BLOB and I just want to see everything else without breaking the formatting.
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