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副标题[/!--empirenews.page--]
我在我的数据库中有几个表,并使用左外连接来连接表并执行查询.问题是,并非所有匹配的记录都被返回,第一个记录总是因某种原因从结果中被跳过.
这是SQL Fiddle的链接,
架构测试数据：
mysql> select * from main;
+----------+------------+----------------+---------------+-------------+-------------+----------------+----------------+-----------------+------------+------------+----------------+-----------------+---------------+--------------------------+--------------+
| username | date | water_quantity | water_chilled | smoked_what | smoke_count | sleep_duration | study_duration | screen_duration | loud_level | heat_level | humidity_level | stress_physical | stress_mental | stress_notes | menstruation |
+----------+------------+----------------+---------------+-------------+-------------+----------------+----------------+-----------------+------------+------------+----------------+-----------------+---------------+--------------------------+--------------+
| test123 | 2012-09-16 | 1 | no | cigarettes | 20 | 480 | 0 | 420 | 2 | 7 | 7 | 6 | 4 | Roamed a lot on the bike | no |
| test123 | 2012-09-13 | 2 | no | cigarettes | 12 | 300 | 0 | 0 | 1 | 1 | 1 | 6 | 3 | met friends | no |
+----------+------------+----------------+---------------+-------------+-------------+----------------+----------------+-----------------+------------+------------+----------------+-----------------+---------------+--------------------------+--------------+
2 rows in set (0.00 sec)
mysql> select * from food;
+----------+------------+--------------+
| username | date | food |
+----------+------------+--------------+
| test123 | 2012-09-16 | rice |
| test123 | 2012-09-16 | pizza |
| test123 | 2012-09-16 | french fries |
| test123 | 2012-09-16 | burger |
| test123 | 2012-09-13 | naan |
| test123 | 2012-09-13 | fried rice |
| test123 | 2012-09-13 | lemon juice |
+----------+------------+--------------+
7 rows in set (0.00 sec)
mysql> select * from alcohol;
+----------+------------+--------------+------------------+
| username | date | alcohol_type | alcohol_quantity |
+----------+------------+--------------+------------------+
| test123 | 2012-09-16 | beer | 0 |
| test123 | 2012-09-16 | beer_ale | 0 |
| test123 | 2012-09-16 | absinthe | 0 |
| test123 | 2012-09-13 | rum | 0 |
| test123 | 2012-09-13 | tequila | 0 |
+----------+------------+--------------+------------------+
5 rows in set (0.00 sec)
mysql> select * from headache;
+----------+------------+-----------+----------+---------------------+
| username | date | intensity | duration | notes |
+----------+------------+-----------+----------+---------------------+
| test123 | 2012-09-16 | 6 | 12 | something something |
+----------+------------+-----------+----------+---------------------+
1 row in set (0.00 sec)
mysql> select * from headache_areas;
+----------+------------+-----------------+
| username | date | area |
+----------+------------+-----------------+
| test123 | 2012-09-16 | left_temple |
| test123 | 2012-09-16 | right_temple |
| test123 | 2012-09-16 | behind_left_ear |
+----------+------------+-----------------+
3 rows in set (0.00 sec)
mysql> select * from headache_symptoms;
+----------+------------+-----------+
| username | date | symptoms |
+----------+------------+-----------+
| test123 | 2012-09-16 | aura |
| test123 | 2012-09-16 | vertigo |
| test123 | 2012-09-16 | dizziness |
+----------+------------+-----------+
3 rows in set (0.00 sec)
mysql> select * from alcohol;
+----------+------------+--------------+------------------+
| username | date | alcohol_type | alcohol_quantity |
+----------+------------+--------------+------------------+
| test123 | 2012-09-16 | beer | 0 |
| test123 | 2012-09-16 | beer_ale | 0 |
| test123 | 2012-09-16 | absinthe | 0 |
| test123 | 2012-09-13 | rum | 0 |
| test123 | 2012-09-13 | tequila | 0 |
+----------+------------+--------------+------------------+
5 rows in set (0.00 sec)
mysql> select * from drugs;
+----------+------------+----------+
| username | date | drug |
+----------+------------+----------+
| test | 2012-08-21 | crocin |
| test | 2012-08-21 | azithral |
| test | 2012-08-21 | crocin |
| test | 2012-08-21 | azithral |
| test | 2012-08-21 | crocin |
| test | 2012-08-21 | azithral |
| test123 | 2012-09-13 | ching |
| test123 | 2012-09-13 | chong |
| test123 | 2012-09-13 | blah1 |
| test123 | 2012-09-13 | blurg2 |
+----------+------------+----------+
10 rows in set (0.00 sec)
查询我尝试了结果：
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