Dynamical column names depending on the single row of the query result - php

Question

I need some help with dynamical column names in a sql query. First I will try to explain my database structure and then the problem.
Database structure:
admin_group table:
+--------+----------------+
| id | language_code |
+--------+----------------+
| 1 | en_UK |
| 2 | de_DE |
| 3 | es_ES |
+--------+----------------+
constructions_meta table:
+--------+-----------------+----------+
| id | admin_group_FK | value |
+--------+-----------------+----------+
| 1 | 1 | 0.13 |
| 2 | 2 | 0.12 |
| 3 | 3 | 0.10 |
+--------+-----------------+----------+
construction_lang table:
+--------+-----------------+----------------+----------------+
| id | en_UK_name | de_DE_name |es_ES_name |
+--------+-----------------+----------------+----------------+
| 1 | Construction 1 | Konstruktion 1 | Construcción 1 |
| 2 | Construction 2 | Konstruktion 2 | Construcción 2 |
| 3 | Construction 3 | Konstruktion 3 | Construcción 3 |
+--------+-----------------+----------------+----------------+
Those are my tables in the database. What I need here is to get the names of the constructions regarding the language code for each construction. For example I want to list the constructions as following:
Construction 1
Konstruktion 2
Construcción 3

Answer 1

select c.id , (select case c.admin_group_FK
when 1 then l.en_UK_name
when 2 then l.de_DE_name
else l.es_ES_name
end from construction_lang l where id = c.id) as construction_name,
c.value
from constructions_meta c;
Yes the solution is only a get-you-working-quickly one .
And Rob is correct about improving the data model
Solution is :
you need to and drop the construction_lang table from your data model and replace it with this association table much like what Rob proposes
+------------------+--------------+----------------+
| construction_fk | language_fk | name |
+------------------+--------------+----------------+
| 1 | 1 | Construction 1 |
| 1 | 2 | Konstruktion 1 |
| 1 | 3 | Construcción 1 |
| 2 | 1 | Construction 2 |
| 2 | 2 | Konstruktion 2 |
| 2 | 3 | Construcción 2 |
| 3 | 1 | Construction 3 |
| 3 | 2 | Konstruktion 3 |
| 3 | 3 | Construcción 3 |
+------------------+--------------+----------------+
then query you require is
select c.id, l.language_code , a.name ,c.value
from constructions_meta c
join construction_lang_assoc a on a.construction_fk = c.id and a.language_fk = c.admin_group_FK
join admin_group l on l.id = c.admin_group_FK;

Answer 2

It's probably easiest to do that in two passes. That'll give you the ability to expand the width of the construction_lang table without affecting the SQL statements significantly.
Firstly you issue a SQL statement to get the column names that you need, then you use that result set to build a second SQL statement that will get the names for you.
This is not the ideal solution, as it is working around the data-model.
Given a query that returns back the id and language from admin_group in line with:
array( array( 'id' => 1, 'language_code' => 'en_UK' ),
array( 'id' => 2, 'language_code' => 'de_DE' ),
array( 'id' => 3, 'language_code' => 'es_ES' ) )
You can build a statement with something along the lines of (using the other answer from diarmuid as an example)
$sql = "select c.id , (select case c.admin_group_FK\r\n";
foreach( $languages as $thisLanguage ) {
$sql .= "when {$thisLanguage['id']} then l.${thisLanguage['language_code']}_name\r\n";
}
$sql .= ...
This is a round-about way of doing it, because of the data-model you have. Ideally you wouldn't need the "dynamic" SQL."
If you want to remove the round-about-ness, and build something more in line with standard relational database theory, then you can change the model so that the construction_lang table is more like this:
+------------------------+-----------------+----------------+
| constructions_meta_fk | language | name |
+------------------------+-----------------+----------------+
| 1 | en_UK | Construction 1 |
| 1 | de_DE | Konstruktion 1 |
| 1 | es_ES | Construcción 1 |
| 2 | en_UK | Construction 2 |
| 2 | de_DE | Konstruktion 2 |
| 2 | es_ES | Construcción 2 |
| 3 | en_UK | Construction 3 |
| 3 | de_DE | Konstruktion 3 |
| 3 | es_ES | Construcción 3 |
+------------------------+-----------------+----------------+

Answer 3

you can use if condtion like `
if(admin_group_FK == 1)
{
fetch['en_UK_name'];
}
if(admin_group_FK == 2)
{
fetch['de_DE_name'];
}
if(admin_group_FK == 3)
{
fetch['es_ES_name'];
}
`