MySQL 视图中的 BLOB 而不是正确的数据

Question

我使用 UNION ALL 从两个表创建了一个 MySQL 视图，以便我可以为这些表中的相同数据获得相同的列名（即 tbl1.author2 AStranslator .. tbl2.translator AStranslator）等等，问题是当我尝试从该视图中选择某些内容时，一半的数据显示为 BLOB，而不是 .原始值。

视图定义是：

SELECT e.id AS prod_id, 
e.price_vat AS price_vat, 
e.product AS title, 
e.authors AS author, 
e.isbn AS isbn, 
e.ean AS ean, 
e.page_count AS page_count, 
e.publishers AS publishers, 
e.issue_year AS issue_year,
'e' AS type
FROM ama_euromedia_products AS e
UNION ALL
SELECT
k.publishers AS publishers, 
DATE_FORMAT(k.publication_date, '%Y') AS issue_year,
k.ean AS ean, 
k.number_of_pages AS page_count, 
k.author AS author, 
k.isbn AS isbn, 
k.title_full AS title, 
k.price_amount AS price_vat, 
k.internal AS prod_id,
'k' AS type
FROM ama_kosmas_products AS k 

表定义：

CREATE TABLE `ama_euromedia_products` (
  `id` int(9) NOT NULL,
  `product` text COLLATE utf8_czech_ci NOT NULL,
  `isbn` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `authors` text COLLATE utf8_czech_ci,
  `publishers` text COLLATE utf8_czech_ci,
  `price` float(9,0) DEFAULT NULL,
  `price_vat` float(9,0) DEFAULT NULL,
  `vat` int(3) DEFAULT NULL,
  `availability` tinyint(1) DEFAULT NULL,
  `genres` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `ean` bigint(14) DEFAULT NULL,
  `page_count` int(7) DEFAULT NULL,
  `issue_year` int(4) DEFAULT NULL,
  `supply_date` timestamp NULL DEFAULT NULL,
  `width` int(7) DEFAULT NULL,
  `height` int(7) DEFAULT NULL,
  `weight` int(7) DEFAULT NULL,
  `binding` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `long_v` text COLLATE utf8_czech_ci,
  `short` text COLLATE utf8_czech_ci,
  `imgurl` text COLLATE utf8_czech_ci,
  `is_preliminary` tinyint(1) DEFAULT NULL,
  `stack_date` timestamp NULL DEFAULT NULL ON UPDATE CURRENT_TIMESTAMP,
  `invoice_only` tinyint(1) DEFAULT NULL,
  `new` tinyint(1) DEFAULT NULL,
  `sale` tinyint(1) DEFAULT NULL,
  `return_v` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `indexy` (`id`,`isbn`,`genres`,`ean`,`issue_year`,`supply_date`,`stack_date`,`new`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_czech_ci;


CREATE TABLE `ama_kosmas_products` (
  `id` int(7) NOT NULL AUTO_INCREMENT,
  `internal` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `isbn` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `ean` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `contained_items` text COLLATE utf8_czech_ci,
  `title_original` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `title_full` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `subtitle` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `other_text` text COLLATE utf8_czech_ci,
  `languages` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `author` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `illustrator` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `translator` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `number_of_pages` int(7) DEFAULT NULL,
  `subject_scheme_name` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `subject_code` int(7) DEFAULT NULL,
  `subject_heading_text` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `media_file_label` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `media_file_thumbnail` varchar(255) COLLATE utf8_czech_ci DEFAULT NULL,
  `publishers` text COLLATE utf8_czech_ci,
  `publishing_status` tinyint(2) DEFAULT NULL,
  `publication_date` timestamp NULL DEFAULT NULL,
  `product_availability` tinyint(2) DEFAULT NULL,
  `on_hand` int(7) DEFAULT NULL,
  `on_order` int(7) DEFAULT NULL,
  `price_amount` int(7) DEFAULT NULL,
  `price_tax_rate_code` varchar(1) COLLATE utf8_czech_ci DEFAULT NULL,
  `price_tax_rate_percent` tinyint(2) DEFAULT NULL,
  `price_tax_amount` int(7) DEFAULT NULL,
  `price_taxable_amount` int(7) DEFAULT NULL,
  `reissue_date` timestamp NULL DEFAULT NULL,
  `invoice_only` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `internal` (`internal`)
) ENGINE=MyISAM AUTO_INCREMENT=43341 DEFAULT CHARSET=utf8 COLLATE=utf8_czech_ci;

知道为什么会这样吗？

Answer 1

当您使用UNION 创建视图时，您必须确保相应列的数据类型相同（或者至少足够相似，以便将一列转换为另一列）。在当前情况下，视图的第一列是 publishers 或 price_vat，除了 BLOB 之外，没有任何数据类型定义可以发挥作用的感觉。

如果您确实需要将其作为视图，您可以尝试...

SELECT e.price_vat AS price_vat, 
       NULL        AS publishers,
       ...etc...
       'e'         AS type
    FROM ama_euromedia_products AS e;
UNION ALL
SELECT
     NULL         AS price_vat,
     k.publishers AS publishers, 
     ...etc...
     'k'          AS type
     FROM ama_kosmas_products AS k;

在每列中获取单一数据类型。