Question

我正在寻找一个SELECT-JOIN语句，该语句可以精确地重现MERGE语句，以便可视化SOURCE表和TARGET表之间完成的精确匹配。

以其他方式，JOIN是哪种？完全加入？全部加入？内部联接？依此类推。

谢谢。

Answer 1

发表声明：

FULL OUTER JOIN

这可能是SELECT COALESCE( dst.some_columns, src.some_columns ) AS some_columns, NVL2( dst.some_columns, dst.columns_to_update_from, columns_to_update ) AS columns_to_update FROM source src FULL OUTER JOIN destination dst ON ( dst.some_columns = src.some_columns )：

LEFT OUTER JOIN

也可以是UNION和-- WHEN MATCHED OR WHEN NOT MATCHED IN DESTINATION SELECT src.some_columns, NVL2( dst.some_columns, dst.columns_to_update_from, columns_to_update ) AS columns_to_update FROM source src LEFT OUTER JOIN destination dst ON ( dst.some_columns = src.some_columns ) UNION ALL -- WHEN NOT MATCHED IN SOURCE SELECT some_columns, columns_to_update_from FROM destination dst WHERE NOT EXISTS ( SELECT 1 FROM source src WHERE ( dst.some_columns = src.some_columns ) )：

INNER JOIN

也可以是UNION和-- WHEN MATCHED SELECT src.some_columns, dst.columns_to_update_from AS columns_to_update FROM source src INNER JOIN destination dst ON ( dst.some_columns = src.some_columns ) UNION ALL -- WHEN NOT MATCHED IN DESTINATION SELECT some_columns, columns_to_update FROM source src WHERE NOT EXISTS ( SELECT 1 FROM destination dst WHERE ( dst.some_columns = src.some_columns ) ) UNION ALL -- WHEN NOT MATCHED IN SOURCE SELECT some_columns, columns_to_update_from FROM destination dst WHERE NOT EXISTS ( SELECT 1 FROM source src WHERE ( dst.some_columns = src.some_columns ) )：

foreach ($_items as $_item):
    echo "<pre>";
    var_dump($_item->debug());
    echo "</pre>";

哪种JOIN语句可以重现Oracle MERGE语句？

1 个答案: