ruby - 修改 ruby​​ 代码以使用 Postgresql

Question

我以前使用 sqlite3 作为我的 ruby​​ 代码，它适用于以下代码

def existsCheck( db, id )
    temp = db.exec( 'SELECT 1 WHERE EXISTS(
        SELECT 1
        FROM Products
        WHERE promoID = ?
    ) ', [id] ).length > 0
end


def writeDB( db, product )
    db.exec( 'INSERT INTO Products ( promoID, name, price, shipping, condition, grade, included, not_included, image, time_added )
                        VALUES ( ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)', [product.promoID, product.name, product.price, product.shipping, product.condition, product.grade, product.included, product.notIncluded, product.image, product.time] )
end

Postgresql 不支持“？”的想法？还是我做错了什么？

Answer 1

来自精美PG::Connection手册：

- (PG::Result) exec(sql[, params, result_format ])
- (Object) exec(sql[, params, result_format ]) {|pg_result| ... }
[...]
PostgreSQL 绑定参数在 SQL 查询中表示为$1、$1、$2等。params 数组的第 0 个元素绑定到$1，第一个元素绑定到$2，依此nil类推NULL。

所以你想在 PostgreSQL 中使用编号占位符：

def existsCheck( db, id )
    temp = db.exec( 'SELECT 1 WHERE EXISTS(
        SELECT 1
        FROM Products
        WHERE promoID = $1
    ) ', [id] ).to_a.length > 0
    # You'll also need to .to_a the result before you can
    # treat it as an array...
end