MYSQL:从其他表插入数据
我正在尝试插入另外两个表中的数据。我目前有两个表,t1和t2: t1: 和t2:MYSQL:从其他表插入数据,mysql,sql,case,Mysql,Sql,Case,我正在尝试插入另外两个表中的数据。我目前有两个表,t1和t2: t1: 和t2: A B C col1 4 99 81 col2 50 26 38 col3 36 38 11 col4 16 49 70 col5 42 83 93 我的目标是形成一个新表,该表仅使用t1和t2中的数据,并形成一个新表,如: col1 col2 col3 col4 col5 4 50 38 16
A B C
col1 4 99 81
col2 50 26 38
col3 36 38 11
col4 16 49 70
col5 42 83 93
我的目标是形成一个新表,该表仅使用t1和t2中的数据,并形成一个新表,如:
col1 col2 col3 col4 col5
4 50 38 16 93
99 26 11 70 42
99 38 38 49 42
81 50 36 16 83
我一直在使用CASE函数,但在附加表时遇到了问题。有什么建议吗
谢谢 如果我们将
t2
从宽表转换为长表:
mysql> CREATE VIEW tidyt2 AS
SELECT x as 'col', 'A' as 'label', A 'value' FROM t2
UNION SELECT x as 'col', 'B' as 'label', B 'value' FROM t2
UNION SELECT x as 'col', 'C' as 'label', C 'value' FROM t2;
Query OK, 0 rows affected (0.03 sec)
mysql> select * from tidyt2;
+------+-------+-------+
| col | label | value |
+------+-------+-------+
| col1 | A | 4 |
| col2 | A | 50 |
| col3 | A | 36 |
| col4 | A | 16 |
| col5 | A | 42 |
| col1 | B | 99 |
| col2 | B | 26 |
| col3 | B | 38 |
| col4 | B | 49 |
| col5 | B | 83 |
| col1 | C | 81 |
| col2 | C | 38 |
| col3 | C | 11 |
| col4 | C | 70 |
| col5 | C | 93 |
+------+-------+-------+
15 rows in set (0.00 sec)
然后,可以使用左联接表示所需的表:
mysql> SELECT t21.value as 'col1'
, t22.value as 'col2'
, t23.value as 'col3'
, t24.value as 'col4'
, t25.value as 'col5'
FROM t1
LEFT JOIN tidyt2 as t21 ON t1.col1 = t21.label AND t21.col='col1'
LEFT JOIN tidyt2 as t22 ON t1.col2 = t22.label AND t22.col='col2'
LEFT JOIN tidyt2 as t23 ON t1.col3 = t23.label AND t23.col='col3'
LEFT JOIN tidyt2 as t24 ON t1.col4 = t24.label AND t24.col='col4'
LEFT JOIN tidyt2 as t25 ON t1.col5 = t25.label AND t25.col='col5';
+------+------+------+------+------+
| col1 | col2 | col3 | col4 | col5 |
+------+------+------+------+------+
| 4 | 50 | 38 | 16 | 93 |
| 99 | 26 | 11 | 70 | 42 |
| 99 | 38 | 38 | 49 | 42 |
| 81 | 50 | 36 | 16 | 83 |
+------+------+------+------+------+
4 rows in set (0.00 sec)
你能在编程语言层面上解决这个问题吗?。有时mysql会承受太大的压力。我使用的语言(python)可以解决这个问题,但mysql是我的第一选择。为什么需要将数据存储在新表中。你为什么不选择你拥有的数据呢?Dan,我想稍后使用新表,并认为形成完整的新表会更容易。我完全是sql新手,也许多做一张表是愚蠢的。但是,如何在这里选择数据有什么建议吗?谢谢丹和罗曼的回复!我认为这可以很容易地用R解决。
mysql> SELECT t21.value as 'col1'
, t22.value as 'col2'
, t23.value as 'col3'
, t24.value as 'col4'
, t25.value as 'col5'
FROM t1
LEFT JOIN tidyt2 as t21 ON t1.col1 = t21.label AND t21.col='col1'
LEFT JOIN tidyt2 as t22 ON t1.col2 = t22.label AND t22.col='col2'
LEFT JOIN tidyt2 as t23 ON t1.col3 = t23.label AND t23.col='col3'
LEFT JOIN tidyt2 as t24 ON t1.col4 = t24.label AND t24.col='col4'
LEFT JOIN tidyt2 as t25 ON t1.col5 = t25.label AND t25.col='col5';
+------+------+------+------+------+
| col1 | col2 | col3 | col4 | col5 |
+------+------+------+------+------+
| 4 | 50 | 38 | 16 | 93 |
| 99 | 26 | 11 | 70 | 42 |
| 99 | 38 | 38 | 49 | 42 |
| 81 | 50 | 36 | 16 | 83 |
+------+------+------+------+------+
4 rows in set (0.00 sec)