Mysql dyanmic value as alias

问题

So the following works

$query = "SELECT 
        A.entity_id,
        B.value AS variable_character,
        C.value AS text,
        D.value AS integer
    FROM customer_address_entity AS A 
    LEFT JOIN customer_address_entity_varchar AS B 
        ON B.entity_id = A.entity_id
    LEFT JOIN customer_address_entity_text AS C 
        ON C.entity_id = A.entity_id
    LEFT JOIN customer_address_entity_int AS D 
        ON A.entity_id = D.entity_id
    ORDER BY A.entity_id DESC
    LIMIT 100";

However there are many values that need to be joined to the entity in table A and right now they are all creating their own nested array based on the new value.

0 => 
array (size=4)
  'entity_id' => string '597424' (length=6)
  'variable_character' => string 'Dave' (length=4)
  'text' => string '45 Haven Rd' (length=11)
  'intiger' => string '43' (length=2)
1 => 
array (size=4)
  'entity_id' => string '597424' (length=6)
  'variable_character' => null
  'text' => string '45 Haven Rd' (length=11)
  'intiger' => string '43' (length=2)
2 => 
array (size=4)
  'entity_id' => string '597424' (length=6)
  'variable_character' => string 'Danielson' (length=9)
  'text' => string '45 Haven Rd' (length=11)
  'integer' => string '43' (length=2)
3 => etc
...

Im thinking this is due to the same key name trying to be joined and therefore I would like to use something more dynamic such as another value such as the value of B.attribute_type_id. where I could get an array to look like

array (size=7)
  'entity_id' => string '597424' (length=6)
  '1' => null
  '2' => 'Dave'
  '3' => 'Danielson'
  '4' => '45 Haven Road'
  'text' => string '45 Haven Rd' (length=11)
  'intiger' => string '43' (length=2)

Or even better: the title for the attributes live in another table called eav_attribute and what would really be ideal would be something along the lines of

$query = "SELECT
    A.entity_id,
    B.value AS (SELECT attribute_code FROM eav_attribute WHERE attribute_id = B.attribute_id),
    C.value AS text,
    ...

Is something like this possible? Or am I going about this in the wrong way?

回答1:

Why are you using left join instead of inner join? Also, if you are doing dynamic queries. You should consider using Stored Procedures. You could mount the SQL statement in a variable and then execute. Here's a quick example:

CREATE DEFINER=`YourDBUSER`@`localhost` PROCEDURE `rtYourProcedureName`(IN variable1 int,variable2d varchar(100), sortBy varchar(50), startRow int, ThisSQL varchar(5000), OUT totalRows int)
BEGIN
###start: MySQL is dumb and do not allow default parameter values, set here:
SET @variable1 = IFNULL(variable1 ,'0');
SET @variable2 = IFNULL(variable2 ,'');
SET @sortBy = IFNULL(sortBy ,'');
SET @startRow = IFNULL(startRow ,1);
###end: MySQL is dumb and do not allow default parameter values

set @htwsql = ThisSQL;

set @htwsql = ' SELECT SQL_CALC_FOUND_ROWS STRAIGHT_JOIN t1.field1 ,t2.field2 ';

if @variable1 = 0 then
	set @htwsql := concat(@htwsql, ' from table1 t1');
else 
	set @htwsql := concat(@htwsql,' from table2 t2 w INNER JOIN table1 t1 ');
end if;

set @htwsql := concat(@htwsql, ' where 1 = 1 ');


### sort order
if rtrim(ltrim(@sortBy)) <> '' then
	set @htwsql := concat(@htwsql,char(13), ' ORDER BY ' , cast(@sortBy as char(50)));
end if;

### limit records for pagination
set @htwsql := concat(@htwsql,char(13), ' LIMIT ', StartRow-1 ,',',24);

### just to debug the generated SQL
insert into rtlogtmp (log) select concat ('rtYourProcedureName SQL = ',@htwsql);


PREPARE stmt1 FROM @htwsql; 

EXECUTE stmt1; 

DEALLOCATE PREPARE stmt1;

SELECT FOUND_ROWS() into totalRows;

END

p.s.: Be careful with the names you use as alias. They may be reserved SQL syntax.

来源：https://stackoverflow.com/questions/34625717/mysql-dyanmic-value-as-alias