我需要一些帮助来构建一个 SQL 来获取诸如四个表的“FULL OUTER JOIN”之类的东西。我有这个结构,不能真正修改太多,因为它是一个已经在使用的数据库:
-- ----------------------------
-- Table structure for article
-- ----------------------------
CREATE TABLE `article` (
`ID` int(10) UNSIGNED NOT NULL AUTO_INCREMENT,
`Name` varchar(255) NULL DEFAULT NULL,
PRIMARY KEY (`ID`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3;
INSERT INTO `article` VALUES (1, 'Coffeemaker');
INSERT INTO `article` VALUES (2, 'Toaster');
-- ----------------------------
-- Table structure for language
-- ----------------------------
CREATE TABLE `language` (
`ID` int(10) UNSIGNED NOT NULL AUTO_INCREMENT,
`Name` varchar(255) NULL DEFAULT NULL,
PRIMARY KEY (`ID`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3;
INSERT INTO `language` VALUES (1, 'German');
INSERT INTO `language` VALUES (2, 'English');
-- ----------------------------
-- Table structure for property
-- ----------------------------
CREATE TABLE `property` (
`ID` int(10) UNSIGNED NOT NULL AUTO_INCREMENT,
`Name` varchar(255) NULL DEFAULT NULL,
PRIMARY KEY (`ID`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 3;
INSERT INTO `property` VALUES (1, 'DescriptionText');
INSERT INTO `property` VALUES (2, 'EAN-Code');
-- ----------------------------
-- Table structure for data
-- ----------------------------
CREATE TABLE `data` (
`ArticleID` int(10) UNSIGNED NOT NULL,
`PropertyID` int(10) UNSIGNED NOT NULL,
`LanguageID` int(10) UNSIGNED NOT NULL,
`Value` varchar(255) NULL DEFAULT NULL,
PRIMARY KEY (`ArticleID`, `PropertyID`, `LanguageID`) USING BTREE,
CONSTRAINT `FK_ArticleID` FOREIGN KEY (`ArticleID`) REFERENCES `article` (`ID`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `FK_LanguageID` FOREIGN KEY (`LanguageID`) REFERENCES `language` (`ID`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `FK_PropertyID` FOREIGN KEY (`PropertyID`) REFERENCES `property` (`ID`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE = InnoDB;
INSERT INTO `data` VALUES (1, 1, 1, 'Eine Kaffemaschine');
INSERT INTO `data` VALUES (2, 1, 2, 'A toaster');
SQL: http://sqlfiddle.com/#!9/91dc8/1
我想要得到的是一个新的 VIEW,它包含对所有实体表的连接,显示所有文章、所有属性和所有语言的一行,但如果可用则使用现有数据,如果不可用则使用 null。
这可能吗? SQL 会是什么样子?
最佳答案
你似乎在追求这个......
SELECT a.id articleid
, p.id propertyid
, l.id languageid
, d.value
FROM article a
CROSS -- optional keyword
JOIN property p
CROSS -- optional keyword
JOIN language l
LEFT -- not optional
JOIN data d
ON d.articleid = a.id
AND d.propertyid = p.id
AND d.languageid = l.id;
+-----------+------------+------------+--------------------+
| articleid | propertyid | languageid | value |
+-----------+------------+------------+--------------------+
| 1 | 1 | 1 | Eine Kaffemaschine |
| 2 | 1 | 1 | NULL |
| 1 | 2 | 1 | NULL |
| 2 | 2 | 1 | NULL |
| 1 | 1 | 2 | NULL |
| 2 | 1 | 2 | A toaster |
| 1 | 2 | 2 | NULL |
| 2 | 2 | 2 | NULL |
+-----------+------------+------------+--------------------+
关于MYSQL full join 4表使用引用表,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/62953554/