I have several tables with different numbers and types of columns, and a single column in common.
+--------+---------+------------+-------------+
| person | beardID | beardStyle | beardLength |
+--------+---------+------------+-------------+
+--------+-------------+----------------+
| person | moustacheID | moustacheStyle |
+--------+-------------+----------------+
I want to fetch all the results that match a given value of the shared column. I can do it using multiple select statements like this:
SELECT * FROM beards WHERE person = "bob"
and
SELECT * FROM moustaches WHERE person = "bob"
But this requires multiple mysql API calls, which seems inefficient. I was hoping I could use UNION ALL to get all the results in a single API call, but UNION requires that the tables have the same number and similar type of columns. I could write a SELECT statement that would manually pad the results from each table by adding columns with NULL values, but that would quickly get unmanageable for a few more tables with a few more columns.
I'm looking for a result set roughly like this:
+--------+---------+------------+-------------+-------------+----------------+
| person | beardID | beardStyle | beardLength | moustacheID | moustacheStyle |
+--------+---------+------------+-------------+-------------+----------------+
| bob | 1 | rasputin | 1 | | |
+--------+---------+------------+-------------+-------------+----------------+
| bob | 2 | samson | 12 | | |
+--------+---------+------------+-------------+-------------+----------------+
| bob | | | | 1 | fu manchu |
+--------+---------+------------+-------------+-------------+----------------+
Is there a way to achieve this that's fast and maintainable? Or am I better off running a separate query for each table?
Clarification:
I'm not looking for a cartesian product. I don't want a row for every combination of beard-and-moustache, I want a row for every beard and a row for every moustache.
So if there are 3 matching beards and 2 matching moustaches I should get 5 rows, not 6.
Merging tables by columns. Multiple tables can be merged by columns in SQL using joins. Joins merge two tables based on the specified columns (generally, the primary key of one table and a foreign key of the other).
this should be working fine:
SELECT * FROM `beards` b LEFT OUTER JOIN `mustaches` ON (0) WHERE person = "bob"
UNION ALL
SELECT * FROM `beards` b RIGHT OUTER JOIN `mustaches` ON (0) WHERE person = "bob"
you don't have to handle the columns by yourself. the left and right outer join do this job. unfortunately mysql doesn't have a full join. that's why you have to do it this way with a union
SELECT * FROM `customer` b LEFT OUTER JOIN `charges` ON (0) LEFT OUTER JOIN `day` ON (0)
UNION
SELECT * FROM `customer` b RIGHT OUTER JOIN `charges` ON (0) LEFT OUTER JOIN `day` ON (0)
UNION
SELECT * FROM `customer` b LEFT OUTER JOIN `charges` ON (0) RIGHT OUTER JOIN `day` ON (0)
this is a local test i made
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