Question

我想SELECT JOIN三个表。其中两个具有唯一条目，但是一个可能有多行用于我的主表中的唯一标识符。我希望在我的查询结果中获得多行，如果在表3中有多个条目，但我想只获得不同的值，并且之前没有重复。举个简单的例子，它应该是这样的：

表用户：

+----------+-----------+--------------+
| user_id  | user_name | email        |
+----------+-----------+--------------+
| 1        | name1     | one@ex.tld   |
| 2        | name2     | two@ex.tld   |
| 3        | name3     | three@ex.tld |
+----------+-----------+--------------+

表格信息：

+----------+---------+--------+
| info_id  | user_id | info   |
+----------+---------+--------+
| 1        | 1       | text1  |
| 2        | 2       | text2  |
| 3        | 3       | text3  |
+----------+---------+--------+

表地址：

+------------+--------+----------------+
| address_id | user_id| address_field1 |
+------------+--------+----------------+
| 1          | 1      | City A         |
| 2          | 1      | City B         |
| 3          | 2      | City C         |
| 4          | 2      | City D         |
| 5          | 2      | City E         |
| 6          | 3      | City F         |
+------------+--------+----------------+

我的实际查询是： SELECT u.user_name，u.email，i.info，a.address_field1 来自用户u INNER JOIN info i ON（u.user_id = i.user_id） INNER JOIN地址为ON（u.user_id = a.user_id）;

^^我尝试了LEFT JOIN和JOIN也没有成功。

查询结果：

+-----------+--------------+--------+----------------+
| user_name | email        | info   | address_field1 |
+-----------+--------------+--------+----------------+
| name1     | one@ex.tld   | text1  | City A         |
| name1     | one@ex.tld   | text1  | City B         |
| name2     | two@ex.tld   | text2  | City C         |
| name2     | two@ex.tld   | text2  | City D         |
| name2     | two@ex.tld   | text2  | City E         |
| name3     | three@ex.tld | text3  | City F         |
+-----------+--------------+--------+----------------+

查询结果我尝试实现：

+-----------+--------------+--------+----------------+
| user_name | email        | info   | address_field1 |
+-----------+--------------+--------+----------------+
| name1     | one@ex.tld   | text1  | City A         |
|           |              |        | City B         |
| name2     | two@ex.tld   | text2  | City C         |
|           |              |        | City D         |
|           |              |        | City E         |
| name3     | three@ex.tld | text3  | City F         |
+-----------+--------------+--------+----------------+

我知道这是可能的，但我不知道如何，我不确定我应该搜索什么。有人可以直接把我放在右边吗？

Answer 1

GROUP_CONCAT与GROUP BY结合使用或多或少。
没有SEPARATOR选项的GROUP_CONCAT将生成逗号分隔值

SELECT u.user_name, u.email, i.info, GROUP_CONCAT(address_field1) AS address_field1
FROM user u
INNER JOIN info i ON (u.user_id = i.user_id)
INNER JOIN address a ON (u.user_id = a.user_id)
GROUP BY u.user_name, u.email, i.info

Answer 2

随意浏览此SQLFiddle以进一步测试此查询及其输出！

cu.accept(new ASTVisitor()
{
    public boolean visit(MethodInvocation inv)
    {               
        if (inv.getExpression() instanceof Name
                        && ((Name) inv.getExpression()).resolveBinding().getKind() == IBinding.TYPE)
        {
            // Static call
        }
        else
        {
            // Non-static call
        }
        return true;
    }
});

谢谢！
奥马尔。

Answer 3

我决定自定义API，并会存储以下几个地址数据：

+-----------+--------------+--------+----------------+----------------+----------------+
| user_name | email        | info   | address_field1 | address_field2 | address_field3 |
+-----------+--------------+--------+----------------+----------------+----------------+
| name1     | one@ex.tld   | text1  | City A         | City B         |                |
| name2     | two@ex.tld   | text2  | City C         | City D         | City E         |
| name3     | three@ex.tld | text3  | City F         |                |                |
+-----------+--------------+--------+----------------+----------------+----------------+

Answer 4

在标准SQL中使用public static void waitForPageLoaded(WebDriver webDriver) { ExpectedCondition<Boolean> expectation = new ExpectedCondition<Boolean>() { public Boolean apply(WebDriver driver) { return ((JavascriptExecutor) driver).executeAsyncScript( "var callback = arguments[arguments.length - 1];" + "if (document.readyState !== 'complete') {" + " callback('document not ready');" + "} else {" + " try {" + " var testabilities = window.getAllAngularTestabilities();" + " var count = testabilities.length;" + " var decrement = function() {" + " count--;" + " if (count === 0) {" + " callback('complete');" + " }" + " };" + " testabilities.forEach(function(testability) {" + " testability.whenStable(decrement);" + " });" + " } catch (err) {" + " callback(err.message);" + " }" + "}" ).toString().equals("complete"); } }; try { WebDriverWait wait = new WebDriverWait(webDriver, waitSeconds); wait.until(expectation); } catch (Throwable error) { new Exception("Timeout waiting for Page Load Request to complete."); } }或LAG可以轻松地抑制重复数据，但MySQL也没有。

您可以做的是再次在地址表中查找第一个地址：

ROW_NUMBER

MYSQL JOIN多个表，避免重复行上的重复条目

4 个答案: