I have inherited a MySQL database, that has a table as follows:
mysql> describe stock_groups;
+--------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| group | varchar(5) | YES | | NULL | |
| name | varchar(255) | YES | | NULL | |
| parent | varchar(5) | YES | | NULL | |
| order | int(11) | YES | | NULL | |
+--------+--------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)
When I run mysql> select * from stock_groups where
group ='D2';
I get:
mysql> select * from stock_groups where `group`='D2';
+----+-------+------+--------+-------+
| id | group | name | parent | order |
+----+-------+------+--------+-------+
| 79 | D2 | MENS | D | 51 |
+----+-------+------+--------+-------+
1 row in set (0.00 sec)
and also i have a table:
mysql> describe stock_groups_styles_map;
+-------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| group | varchar(5) | NO | | NULL | |
| style | varchar(25) | NO | | NULL | |
+-------+-------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
when I run:
mysql> select `group` from stock_groups_styles_map where style='N26';
+-------+
| group |
+-------+
| B1 |
| B11 |
| D2 |
| V2 |
+-------+
4 rows in set (0.00 sec)
how do i get the stock_groups.name
?
Join the tables, and select only the data you need. If you need unique rows, use the distinct
keyword:
select -- If you need unique names, use "select distinct" instead of "select"
sg.name
from
stock_groups_styles_map as sgs
inner join stock_groups as sg on sgs.group = sg.group
where
sgs.style = 'N26'
You could also solve this using subqueries, but that would be rather inneficient in this case.
Something important
You should add the appropriate indexes to your tables. It will improve the performance of your database.
You can use inner join on group column
SELECT ss.group, sg.name from
stock_groups sg inner join stock_groups_styles_map ss on ss.group = sg.group
where ss.style='N26'
SELECT stock_groups.name FROM stock_groups_styles_map, stock_groups WHERE stock_groups_styles_map.style ='N26';
为我工作。
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