MySQL 过程 : If column don't exists create it

Question

我尝试创建在 MySQL 表中创建不存在列的过程，如下所示: MySQL add column if not exist

我的程序:

DELIMITER $$
CREATE PROCEDURE Alter_Table(IN _table_name TEXT,IN _column_name TEXT,IN _column_type TEXT)
BEGIN
    DECLARE _count INT;
    SET _count = (  SELECT COUNT(*) 
                    FROM INFORMATION_SCHEMA.COLUMNS
                    WHERE   TABLE_NAME = _table_name AND 
                            COLUMN_NAME = _column_name);
    IF _count = 0 THEN
        ALTER TABLE _table_name ADD COLUMN _column_name _column_type;
    END IF;
END $$
DELIMITER ;

但是我有一个错误:

#1064 - Something is wrong in your syntax obok '_column_type; END IF; END' w linii 9

有人知道为什么吗？

Answer 1

好的...我用 PHP 制作...

function alter_table($table_name, $column_name, $column_type) {
    $result = mysql_query("SELECT * FROM INFORMATION_SCHEMA.COLUMNS
                 WHERE TABLE_NAME = `$table_name` AND COLUMN_NAME = `$column_name`");
    if(!$result) {
        mysql_query("ALTER TABLE `$table_name`
            ADD COLUMN `$column_name` $column_type");
    }
}