Mysql CASE statement usage with Zend

问题

I have the following query that selects some records from the database:

$select_person = $this->select()
        ->setIntegrityCheck(false)
        ->from(array('a' => 'tableA'), 
                array(new Zend_Db_Expr('SQL_CALC_FOUND_ROWS a.id'),
                        'a.cid',  
                        'a.email',
                        'final' => new Zend_Db_Expr( "concat( '<div 
                            style=\"color:#1569C7; font-weight:bold\">',
                            a.head , ' ' ,  a.tail,  '</div>')" ),
                        'a.red_flag'
                )
        )   
        ->joinLeft(array('b' => 'tableb'), ... blah blah)
        ->where('blah blah')
        ->order('a.head ASC')

I want to modify the above query so that it selects a different value for 'final' depending on the value of

a.red_flag.

which can have values - true or false.

I understand I can use the CASE statement of mysql - eg something like the following:

'final' => new Zend_Db_Expr("CASE a.red_flag WHEN 'true' THEN '$concatstr1'
                        ELSE '$concatstr2' END")

The value of $concatstr1 = "concat( '<div style=\"color:red; font-weight:bold\">', a.head , ' ' , a.tail, '</div>')" ;

The value of $concatstr2 = "concat( '<div style=\"color:blue; font-weight:bold\">', a.head , ' ' , a.tail, '</div>')" ;

However, it throws an error saying

Message: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'div style="color:red; font-weight:bold">', a.head , ' ' , ' at line 1

How can I make this query work? Any help is greatly appreciated.

Thanks

回答1:

Personnaly, I don't like to get HTML as an answer from the DB. It gets confusing and harder to debug and change afterwards. Furthermore, you might get some errors due to the confusion with the ' and " and all the reserved characters in MySQL (<, >, ;, ...) I would suggest that you try this:

'final' => new Zend_Db_Expr("CASE a.red_flag WHEN 'true' THEN 1
                        ELSE 0 END")

Then do a check on the value of a.red_flag;

if($this->final) {
    $output .= '<div style=\"color:red; font-weight:bold\">';
} else {
    $output .= '<div style=\"color:blue; font-weight:bold\">';
}
$output .= $this->head.' '.$this->tail;
$output .= '</div>';

If the query still doesn't work. Try

echo $select->__toString; exit();

and check the query. Try the output that you got with the __toString on your database and check if it works. It's easier to fix it that way. You could also show the query string here and it'll be easier to debug.

回答2:

Finally, I found the error in my statement. The culprit was - I was using quotes in $concatstr1 and $concatstr2 inside the $select_person statement. The correct query should be formed as follows:

$select_person = $this->select()
        ->setIntegrityCheck(false)
        ->from(array('a' => 'tableA'), 
                array(new Zend_Db_Expr('SQL_CALC_FOUND_ROWS a.id'),
                        'a.cid',  
                        'a.email',
                        final' => new Zend_Db_Expr("CASE a.red_flag WHEN 'true' THEN $concatstr1 ELSE $concatstr2 END"),
                        'a.red_flag'
                )
        )   
        ->joinLeft(array('b' => 'tableb'), ... blah blah)
        ->where('blah blah')
        ->order('a.head ASC');

This is now returning me the appropriate value of 'final' - concatstr1 when red_flag is true otherwise it is returning me concatstr2.

来源：https://stackoverflow.com/questions/11680451/mysql-case-statement-usage-with-zend

标签

mysql

zend-framework

case