Question

需要查询帮助：

Id  Name  Balance
1   A     10
2   A     -10
3   A     10
4   A     15
5   B     10.5
6   B     -10.5
7   B     25

要求：我想删除每个名称的+ ve和-ve值的余额。我期待以下输出

预期结果： -

Id Name Balance
1  A    10
2  A    15
3  B    25

请与我分享SQL查询。

Answer 1

这是一种方法。

创建用于测试的虚拟数据

CREATE TABLE foo (Id INT, Name VARCHAR(50), Balance money);
INSERT INTO foo VALUES (1, 'A', 10);
INSERT INTO foo VALUES (2, 'A', -10);
INSERT INTO foo VALUES (3, 'A', 10);
INSERT INTO foo VALUES (4, 'A', 15);
INSERT INTO foo VALUES (5, 'B', 10.5);
INSERT INTO foo VALUES (6, 'B', -10.5);
INSERT INTO foo VALUES (7, 'B', 25);

1）创建一个临时表，其中有一个额外的MatchFound列来记录是否找到匹配。

CREATE TABLE #TempTable(Id int, Name varchar(50), Balance decimal(10,2), MatchFound bit);
INSERT INTO #TempTable (Id, Name, Balance, MatchFound)
SELECT Id, Name, Balance, 0
FROM foo;

2）遍历数据以查找每行的匹配项。如果找到匹配项，请更新MatchFound列。

DECLARE @Id INT, @Name VARCHAR(50), @Balance decimal(10,2), @MatchId INT;
DECLARE MyCursor CURSOR FOR SELECT Id, Name, Balance FROM #TempTable ORDER BY Id;
OPEN MyCursor

FETCH NEXT FROM MyCursor INTO @Id, @Name, @Balance

WHILE @@FETCH_STATUS = 0
BEGIN
    IF EXISTS (SELECT 1 FROM #TempTable WHERE Id = @Id AND MatchFound = 0)
    BEGIN
        SET @MatchId = NULL
        SELECT TOP 1 @MatchId = Id FROM #TempTable 
        WHERE Id <> @Id AND Name = @Name AND Balance = @Balance * -1 AND MatchFound = 0
        IF @MatchId IS NOT NULL
            UPDATE #TempTable SET MatchFound = 1 WHERE Id IN (@Id, @MatchId)
    END
    FETCH NEXT FROM MyCursor INTO @Id, @Name, @Balance
END
CLOSE MyCursor;
DEALLOCATE MyCursor;

3）选择并返回没有匹配的行

Select Id, Name, Balance From #TempTable Where MatchFound = 0

4）清理

drop table #TempTable

SQL查询获取以下输出

1 个答案: