C# SQL 添加重复键的查询检查

Question

我正在尝试在我当前的 SQL INSERT INTO 语句中添加一个查询。下面是我的表格和当前的 sql 语句。

我有 3 张桌子：

Table1：用户 ID、用户名。

Table2：用户 ID、状态。

Table3：用户 ID、用户名、问题

目前我只有 3 个 SELECT 语句满足上述 3 个检查并将结果插入 Table3：

 1.
    Insert in to Table3(userid,issue)
        SELECT t1.userid,'check no.1'
        FROM table1 t1
        FULL OUTER JOIN table2 t2 ON t1.userid = t2.userid
        where t1.userid not null and t2.userid is null
2.
    Insert in to Table3(userid,issue)
        SELECT t1.userid,'check no.2'
        FROM table1 t1
        inner JOIN table2 t2 ON t1.userid = t2.userid
        where t2.status = 'DELETE'

3.
    Insert in to Table3(userid,issue)
        SELECT t2.userid,'check no.3'
        FROM table2 t2
        right outer JOIN table2 t2 ON t1.userid = t2.userid
        where t2.status <> 'DELETE' and t1.userid is null

现在我想添加另一个额外的检查，即在 T1 和 T2 中检查重复的用户 ID：

1. 检查具有相同大写字母的相同用户 ID（例如 E01 和 E01 不应存在）
2. 检查相同的用户 ID 但不同的大写（例如 E01 和 e01 不应存在）

如何编写专门检查重复用户 ID 的第 4 个 sql 查询？

感谢您的帮助。

Answer 1

唯一的 userId 约束可能最好使用 UNIQUE INDEX 强制执行（应该也有助于提高性能），但为了确保您不要求输入重复项，这应该对您有所帮助：我使用 LEFT JOIN 进入 table3 来检查该值当前为空（记录不存在）

此代码将忽略重复项，并且不插入记录

INSERT INTO Table3(UserId, Username, Issue)
SELECT COALESCE(t1.UserId, t2.UserId), t1.UserName
       , CASE
            WHEN (t2.userid IS NULL AND t1.userid IS NOT NULL)
               THEN 'User exists in t1 but not in t2'
            WHEN (t2.status = 'DELETE' AND t1.userid IS NOT NULL)
               THEN 'User Exists in t1, but status in t2 is DELETED'
            WHEN (t2.userid IS NOT NULL AND t2.status != 'DELETE' AND t1.userid IS NULL)
               THEN 'Non-Deleted user in t2 does not exist in t1'
         END AS Issue
    FROM table1 t1
    FULL OUTER JOIN table2 t2 ON t1.userid = t2.userid
    LEFT JOIN Table3 AS t3user ON t1.UserID = t3user.UserId
    LEFT JOIN Table3 AS t3status ON t2.UserId = t3status.UserId
    WHERE t3user.UserId IS NULL
       AND t3status.UserId IS NULL
       AND
       (
          (t2.userid IS NULL AND t1.userid IS NOT NULL)
          OR (t2.status = 'DELETE' AND t1.userid IS NOT NULL)
          OR (t2.userid IS NOT NULL AND t2.status != 'DELETE' AND t1.userid IS NULL)
       )

如果你想插入一条表示重复的记录，你可以使用以下：

INSERT INTO Table3(UserId, Username, Issue)
SELECT COALESCE(t1.UserId, t2.UserId), t1.UserName
       , CASE
            WHEN (t3user.UserId IS NOT NULL OR t3Status.UserId IS NOT NULL)
               THEN 'Duplicated userid found: "' + t1.UserId + '"'
            WHEN (t2.userid IS NULL AND t1.userid IS NOT NULL)
               THEN 'User exists in t1 but not in t2'
            WHEN (t2.status = 'DELETE' AND t1.userid IS NOT NULL)
               THEN 'User Exists in t1, but status in t2 is DELETE'
            WHEN (t2.userid IS NOT NULL AND t2.status != 'DELETE' AND t1.userid IS NULL)
               THEN 'Non-Deleted user in t2 does not exist in t1'
         END AS Issue
    FROM table1 t1
    FULL OUTER JOIN table2 t2 ON t1.userid = t2.userid
    LEFT JOIN Table3 AS t3user ON t1.UserID = t3user.UserId
    LEFT JOIN Table3 AS t3status ON t2.UserId = t3status.UserId
    WHERE 

       (
          (t2.userid IS NULL AND t1.userid IS NOT NULL)
          OR (t2.status = 'DELETE' AND t1.userid IS NOT NULL)
          OR (t2.userid IS NOT NULL AND t2.status != 'DELETE' AND t1.userid IS NULL)
       )

Answer 2

已编辑：

INSERT INTO Table3(userid, Username, issue)
SELECT 
    userid, Username, 'Duplicate UserID' 
FROM 
    (
        SELECT 
                userid, 
                Username, 
                RANK() OVER (PARTITION BY userid ORDER BY userid) AS [RANK] 
        FROM 
            Table1 --table2
    ) X
WHERE 
    [RANK]=2


INSERT INTO Table3(userid, Username, issue)
SELECT 
    userid, [status], 'Duplicate UserID' 
FROM 
    (
        SELECT 
                userid, 
                [status], 
                RANK() OVER (PARTITION BY userid ORDER BY userid) AS [RANK] 
        FROM 
            Table2
    ) X
WHERE 
    [RANK]=2

如果需要，您可以使用 OLD 部分中所示的 COLLATE 进行区分大小写的检查。

我使用 RANK=2 只为重复的用户 ID 插入一个条目

旧： 您可以使用 COLLATE 进行区分大小写的检查

INSERT INTO Table3(UserId, Username, Issue)
    SELECT 
    COALESCE(t1.UserId, t2.UserId), 
    t1.UserName,
    CASE        
        WHEN (t2.userid IS NULL AND t1.userid IS NOT NULL)
            THEN 'User exists in t1 but not in t2'
        WHEN (t2.status = 'DELETE' AND t1.userid IS NOT NULL)
            THEN 'User Exists in t1, but status in t2 is DELETE'
        WHEN (t2.userid IS NOT NULL AND t2.status != 'DELETE' AND t1.userid IS NULL)
            THEN 'Non-Deleted user in t2 does not exist in t1'
        WHEN t1.userid COLLATE SQL_Latin1_General_CP1_CS_AS = t2.userid COLLATE SQL_Latin1_General_CP1_CS_AS
            THEN 'Duplicate userid with same caps'
        WHEN t1.userid = t2.userid
            THEN 'Duplicate userid but different caps'
     END
FROM table1 t1
FULL OUTER JOIN table2 t2 ON t1.userid = t2.userid
WHERE 
    (t1.userid IS NOT NULL AND t2.userid IS NOT NULL AND t2.status != 'DELETE' AND t1.userid = t2.userid) OR    
    (t2.userid IS NULL AND t1.userid IS NOT NULL) OR 
    (t2.status = 'DELETE' AND t1.userid IS NOT NULL) OR 
    (t2.userid IS NOT NULL AND t2.status != 'DELETE' AND t1.userid IS NULL)

Answer 3

正如人们评论的那样 - 区分大小写是通过排序规则设置的。

至于检查重复键 - 您可以使用 EXISTS keyword。
像这样的：

WHEN EXISTS (SELECT * FROM Table3 WHERE userid=t1.UserID)
   THEN -- DO WHATEVER

但是，如果您愿意禁用插入重复 ID，则应改为设置主键/唯一索引。

编辑： 查询表 1 中的重复项：

Insert into Table3(userid,issue)
SELECT t1.userid,'Duplicate in table1'
FROM Table1 t1
WHERE (SELECT COUNT(*) FROM Table1 _t1 WHERE _t1.userid = t1.userid) > 1

对于表 2 中的重复查询将非常相似。