SQL 查询未返回与其子查询结果所建议的值相同的值

Question

我编写了一个查询，用于查找本周有哪些学生登录了该应用程序。我的 SQLite 查询如下所示：

public static final String WHOLE_QUERY = "SELECT " + DBHelperTest.USER_ID
            + " , " + DBHelperTest.FNAME + " , " + DBHelperTest.SNAME
            + " FROM " + DBHelperTest.TABLE_CHILD + " WHERE "
            + DBHelperTest.USER_ID + " = (SELECT " + DBHelperTest.USER_ID
            + " FROM " + DBHelperTest.TABLE_SESSION_DATA + " WHERE "
            + DBHelperTest.WEEK_OF_YEAR_SIGNED_IN + " = " + theWeek() + " AND "
            + DBHelperTest.YEAR_SIGNED_IN + " = " + theYear() + ") " + " AND "
            + DBHelperTest.USER_ID + " = (" + "SELECT "
            + DBHelperTest.Child_USER_ID + " FROM " + DBHelperTest.TABLE_CLASS
            + " WHERE " + DBHelperTest.Teacher_USER_ID + " = (SELECT "
            + DBHelperTest.USER_ID + " FROM " + DBHelperTest.TABLE_SESSION_DATA
            + " WHERE " + DBHelperTest.SESSION_ID + " = ( SELECT MAX("
            + DBHelperTest.SESSION_ID + ") FROM "
            + DBHelperTest.TABLE_SESSION_DATA + ")))";

它returns没什么。但是，如果我将其分成两个查询...

首先，此查询显示本周登录的所有用户：

public static final String LOGGED_IN_THIS_WEEK_QUERY = "SELECT "
            + DBHelperTest.USER_ID + " , " + DBHelperTest.FNAME + " , "
            + DBHelperTest.SNAME + " FROM " + DBHelperTest.TABLE_CHILD
            + " WHERE " + DBHelperTest.USER_ID + " = (SELECT "
            + DBHelperTest.USER_ID + " FROM " + DBHelperTest.TABLE_SESSION_DATA
            + " WHERE " + DBHelperTest.WEEK_OF_YEAR_SIGNED_IN + " = "
            + theWeek() + " AND " + DBHelperTest.YEAR_SIGNED_IN + " = "
            + theYear() + ") ";

此查询输出用户 ID 为 "Jasm" 的用户。

其次，此查询显示与给定教师关联的所有用户：

   public static final String CHILD_WITH_SAME_TEACHER_QUERY = "SELECT "
                + DBHelperTest.Child_USER_ID + " FROM " + DBHelperTest.TABLE_CLASS
                + " WHERE " + DBHelperTest.Teacher_USER_ID + " = (SELECT "
                + DBHelperTest.USER_ID + " FROM " + DBHelperTest.TABLE_SESSION_DATA
                + " WHERE " + DBHelperTest.SESSION_ID + " = ( SELECT MAX("
                + DBHelperTest.SESSION_ID + ") FROM "
                + DBHelperTest.TABLE_SESSION_DATA + "))";

此查询输出用户 ID 为 "Jasm" 和 "thup" 的用户。

为什么我的原始查询没有输出 "Jasm" 的详细信息，因为此用户满足两个条件？

请参阅下面的更易于阅读的版本：

整个查询：

SELECT USER_ID ,  FNAME , SNAME 
FROM TABLE_CHILD
WHERE USER_ID = 
(
SELECT USER_ID  
FROM TABLE_SESSION_DATA
WHERE WEEK_OF_YEAR_SIGNED_IN = theWeek()  
AND YEAR_SIGNED_IN = theYear()
) 
AND USER_ID = 
(
SELECT Child_USER_ID 
FROM TABLE_CLASS
WHERE Teacher_USER_ID = 
(
SELECT USER_ID 
FROM TABLE_SESSION_DATA
WHERE SESSION_ID = 
( 
SELECT MAX(SESSION_ID) 
FROM TABLE_SESSION_DATA)))

上半场

SELECT USER_ID ,  FNAME , SNAME 
FROM TABLE_CHILD
WHERE USER_ID = 
(
SELECT USER_ID  
FROM TABLE_SESSION_DATA
WHERE WEEK_OF_YEAR_SIGNED_IN = theWeek()  
AND YEAR_SIGNED_IN = theYear()
)

下半场

SELECT Child_USER_ID 
FROM TABLE_CLASS
WHERE Teacher_USER_ID = 
(
SELECT USER_ID 
FROM TABLE_SESSION_DATA
WHERE SESSION_ID = 
( 
SELECT MAX(SESSION_ID) 
FROM TABLE_SESSION_DATA))

Answer 1

尝试使用 "IN" 运算符而不是“=”来 select 多个结果而不是一个。

在您的代码中：

+ DBHelperTest.USER_ID + " IN (SELECT " + DBHelperTest.USER_ID
...
+ DBHelperTest.USER_ID + " IN (" + "SELECT "

Answer 2

嗯，很有趣。我在下面写了这个格式很好的SQL（我已经将日期函数更改为我更熟悉的相应的 T-SQL 函数）。

我没有基础数据来玩这个查询，所以我只能看代码。

这看起来像是一系列独立的（不相关的）子查询，我想乍一看应该可行。

最深的子查询将 return 为 NULL 或单个值。所有其他子查询都使用“=”并且等价运算符不能处理多个值，尽管查看子查询（没有数据）结果集中可能有多个值是可能的吗？也许您只是没有从 SQLite 返回有意义的错误消息？

难道这就是问题所在？比在某处 returned 更有价值？如果您使用“IN”而不是“=”，这可能会变得更加明显吗？

如果没有，您能否 post 一些样本数据，或许可以让问题重现？

SELECT USER_ID, FNAME .SNAME
FROM TABLE_CHILD
WHERE USER_ID =
    (
        SELECT USER_ID
        FROM TABLE_SESSION_DATA
        WHERE WEEK_OF_YEAR_SIGNED_IN  = datepart(week,getdate())
        AND
        YEAR_SIGNED_IN  =  datepart(year,getdate()) 
        AND
        USER_ID =
             (
                SELECT Child_USER_ID
                FROM TABLE_CLASS
                WHERE Teacher_USER_ID =
                        (
                            SELECT USER_ID
                            FROM
                            TABLE_SESSION_DATA
                            WHERE SESSION_ID = 
                                (
                                    SELECT MAX(SESSION_ID)
                                    FROM TABLE_SESSION_DATA
                                )
                         )
              )
    )

SQL 查询未返回与其子查询结果所建议的值相同的值

SQL query not returning same value as its subqueries results would suggest

sql

sqlite

android