CODEWITHSUNDEEP
mysqlstored-procedures
Luckyy
Luckyy

Reputation: 1031

dynamic column name selection in MySql

I am stuck in Mysql today with the dynamic column name need in mysql select statement. Let me explain:

sql> select name1 from namescollection. 
sql> select name2 from namescollection. 
sql> select name3 from namescollection.

So namescollection table has three columns having name1, name2, name3 I would like to query this table in my stored procedure being 1,2,3 as dynamic and would be passed as a variable, but on the simple sql too when i query:

SELECT concat('name','1') FROM `namescollection`

name1 ----- name1 rather fetching name1 field's value.

Can any suggest on this, the right function i need to use rather concat though I know its right to output name1 when I am calling concat but I want to use it as column name.

Upvotes: 6

Views: 16098

Answers (2)

Ajeet Kumar
Ajeet Kumar

Reputation: 166

Dynamic column name in store procedure Update statement :

DELIMITER //
CREATE DEFINER=`root`@`localhost` PROCEDURE `selname`()
BEGIN
    declare cl int ;
    declare clvalue int ;

    set cl=1;
    SET clvalue=1;
    while cl < 4 DO
        SET clvalue=clvalue*cl;
        SET @sql = CONCAT('update test set col',cl, '=',clvalue,' where id=1');
        PREPARE stmt FROM @sql;
        EXECUTE stmt;
        DEALLOCATE PREPARE stmt;
        set cl=cl+1;
   end while;

END //
DELIMITER ;

Upvotes: 5

Zane Bien
Zane Bien

Reputation: 23135

What you can do is use a prepared statement within your stored procedure which will allow you to execute a string query:

As a simple example:

DELIMITER //
CREATE PROCEDURE selname (IN col VARCHAR(20))
BEGIN
  SET @sql = CONCAT('SELECT ', col, ' FROM tbl');
  PREPARE stmt FROM @sql;
  EXECUTE stmt;
  DEALLOCATE PREPARE stmt;
END//
DELIMITER ;

Test it out with this SQLFiddle Demo

Upvotes: 15

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