Question

当前，我正在GetOleDbSchemaTable的帮助下获取表和列。我也想得到给定的列是否必需。

//backend response
const response = {
    data: {
        results: {
            222: {
                items: ['id1', 'id3']
            },
            333: {
                items: ['id2', 'id4', 'id999 (UNKNOWN)']
            }
        }
    }
};

//currently saved in redux state
const stateItems = [
    {
        id: 'id1',
        name: 'item ONE'
    }, {
        id: 'id2',
        name: 'item TWO'
    }, {
        id: 'id3',
        name: 'item THREE'
    }, {
        id: 'id4',
        name: 'item FOUR'
    }, {
        id: 'id5',
        name: 'item FIVE (UNUSED)'
    }, {
        id: 'id6',
        name: 'item SIX (UNUSED)'
    }
];

// Create map of state items (only once each time stateItems changes):
const stateItemMap = new Map(stateItems.map(item => [item.id, item]));

// Map results (each time you get results):
const result = {};
for (const [key, {items}] of Object.entries(response.data.results)) {
    result[key] = {
        items: items.map(id => stateItemMap.get(id))
    };
}

//final result should be:
const expectedFinalResult = {
    222: {items: [{id: 'id1', name: 'item ONE'}, {id: 'id3', name: 'item THREE'}]},
    333: {items: [{id: 'id2', name: 'item TWO'}, {id: 'id4', name: 'item FOUR'}]}
};

//both should be equal:
console.log(JSON.stringify(result, null, 4));

这样我就可以得到给定列的列和数据类型。现在，我想获取列表或使用一种方法可以获取表中的必填字段。

Answer 1

使用GetSchema方法并询问COLUMNS集合将返回一个DataTable，您可以在其中找到IS_NULLABLE属性

using(OleDbConnection con = new OleDbConnection(......)
{ 
    con.Open();
    string[] rest = new string[] { null, null, tableName, null };
    var schema = con.GetSchema("COLUMNS", rest);
    foreach (DataRow row in schema.Rows)
        Console.WriteLine($"Column={row["COLUMN_NAME"]}, NULLABLE={row["IS_NULLABLE"]}");

}

顺便说一句，通过使用您的方法进行检查，GetOleDbSchemaTable返回了相同的数据表，因此，它只是存储在IS_NULLABLE列中的值

从Access数据库获取必需的列

1 个答案: