Question

I am working on some reports and I am trying to create a query that would select a different query depending on the date selected, this is a simplify version of what I am trying to achieve

SELECT *
FROM
    IF(YEAR('###date start###'=2011),table_2011,table)
WHERE
    date_start BETWEEN '###date start###' AND '###date end###'

###date start### and ###date end### are parameters entered by the user.

I cannot use the language to select the different table depending on the date as this is only an example and I might have other parameters passed that would select a different table.

I am thinking that I will need to create a new preg_replace and force the person that create the queries to add something like ###if(test,val2,val2)### but if mysql can already do this I would not like to re-invent the hot-water.

Thank you

EDIT

While waiting for a better solution, I changed the “search replace” function from a simple:
###search### => value (where the ###search### was showing to the end user as a field to manually enter), to also accept a new field formatted like
LLLlabel[option:value,option:value,option:value,....]LLL

Not the best solution as I wish I could do it with MySQL only as this solution is only an annoyance to the end user to have to select an extra parameter.

Please keep in mind that the question is only a VERY simplified version of the query, the query can be part of subqueries, or unions, or joins and not only have a time separation

Answer 1

A stored procedure with the following will work:

DELIMITER //

CREATE PROCEDURE example(date_start DATETIME, date_end DATETIME)
BEGIN
    SET @table = IF(YEAR(date_start)=2011,'table_2011','table');

    SET @sql = CONCAT(
        "SELECT * FROM ",
        @table,
        " WHERE date_start BETWEEN ",
        QUOTE(date_start),
        " AND ",
        QUOTE(date_end)
    ); 

    PREPARE stmt FROM @sql; 
    EXECUTE stmt; 
    DEALLOCATE PREPARE stmt; 
END;
//

DELIMITER ;

and call it via:

CALL example('###date start###', '###date end###');

or if your data is in MyISAM tables, you could set up a MERGE table:

CREATE TABLE all_tables (...) ENGINE = MERGE UNION=(table_2011, table);

SELECT *
FROM
    all_tables
WHERE
    date_start BETWEEN '###date start###' AND '###date end###'