无法从 SQLite 中新创建的列中获取数据

Question

countProductSelect 和 countProductInput 列的当前值 - INTEGER NOT NULL;

需要将INTEGER DEFAULT NULL；

PHP 代码如下。

问题在于，当尝试从时间列和 countProductSelectTmp countProductInputTmp 更新数据和 countProductSelect countProductInput 时，出现错误 - “no such column: countProductSelectTmp”。

如何处理这个错误？或者也许有更多受过教育的算法来解决原始问题？

/**
 * Updating the database
 * 
 * @return bool
 */
protected function _updateDB()
{
    $version = '3.8.4.0';

    $this->_pdo->exec('
        ALTER TABLE data ADD optionalCountProduct INTEGER DEFAULT NULL;
        ALTER TABLE data ADD countProductSelectTmp INTEGER DEFAULT NULL;
        ALTER TABLE data ADD countProductInputTmp INTEGER DEFAULT NULL;
        UPDATE data SET countProductSelectTmp = countProductSelect, countProductInputTmp = countProductInput;
    ');

    $this->_deleteSQLiteColumn(array('countProductSelect', 'countProductInput'));

    // BUG
    // countProductSelect and countProductInput can not get the value countProductSelectTmp and countProductInputTmp
    $this->_pdo->exec('
        ALTER TABLE data ADD countProductSelect INTEGER DEFAULT NULL;
        ALTER TABLE data ADD countProductInput INTEGER DEFAULT NULL;
        UPDATE data SET countProductSelect = countProductSelectTmp, countProductInput = countProductInputTmp;
        UPDATE version SET id = "' . $version . '";
    ');

    $this->_deleteSQLiteColumn(array('countProductSelectTmp', 'countProductInputTmp'));

    return true;
}


/**
 * Remove column from a SQLite Table
 * 
 * @param array $column name of the column to remove
 * @return bool
 */
protected function _deleteSQLiteColumn(array $column)
{
    return (bool)$this->_pdo->exec('
        BEGIN TRANSACTION;
        CREATE TEMPORARY TABLE backup(' . $this->_getFullColumnsString() . ');
        INSERT INTO backup SELECT ' . $this->_getShortColumnsString() . ' FROM data;
        DROP TABLE data;
        CREATE TABLE data(' . $this->_getFullColumnsString($column) . ');
        INSERT INTO data SELECT ' . $this->_getShortColumnsString($column) . ' FROM backup;
        DROP TABLE backup;
        COMMIT;
    ');
}

Answer 1

来自fine manual：

PDO::exec — 执行一条 SQL 语句并返回受影响的行数

但是您试图一次执行多个语句，所以它可能只执行最后一个语句。尝试按预期使用exec 并一次执行一个语句：

$this->_pdo->exec('ALTER TABLE data ADD optionalCountProduct INTEGER DEFAULT NULL');
$this->_pdo->exec('ALTER TABLE data ADD countProductSelectTmp INTEGER DEFAULT NULL');
$this->_pdo->exec('ALTER TABLE data ADD countProductInputTmp INTEGER DEFAULT NULL');
$this->_pdo->exec('UPDATE data SET countProductSelectTmp = countProductSelect, countProductInputTmp = countProductInput');

然后再用你的下一个多语句exec 和你的_deleteSQLiteColumn。

就更好的方法而言，看起来您想要做的只是删除NOT NULL 约束，但SQLite's ALTER TABLE 有点受限，因此您的“添加列、复制列、通过表复制删除列”方法是你能做的最好的；来自SQLite FAQ：

例如，假设您有一个名为“t1”的表，其中列名称为“a”、“b”和“c”，并且您想从该表中删除“c”列。以下步骤说明了如何做到这一点：

BEGIN TRANSACTION;
CREATE TEMPORARY TABLE t1_backup(a,b);
INSERT INTO t1_backup SELECT a,b FROM t1;
DROP TABLE t1;
CREATE TABLE t1(a,b);
INSERT INTO t1 SELECT a,b FROM t1_backup;
DROP TABLE t1_backup;
COMMIT;